feat(rich): 安卓能编辑富文本了，图片直链换成短期签名，表格不再撑破抽屉

三件欠账一次清：

1. 图片直链签名化
   - 新增 `backend/app/services/signing.py`：HMAC-SHA256，密钥由 `JWT_SECRET` 域分离派生
     （`attachment-raw-v1`），载荷 `workspace_id:attachment_id:exp`，默认 30 分钟
   - `/raw` 支持 `?exp=&sig=`，不需要登录态；签名里绑了工作区，跨租户链接直接拒
   - 附件对象多一个 `raw_url`，前端每次渲染现签，正文里只存不带凭据的 `/raw`
   - 保留旧 `?token=` 通道，给未升级的客户端过渡

2. 安卓富文本编辑器
   - `ui/RichTextEditorScreen.kt`：Markdown 工具栏（粗体/斜体/标题/列表/引用/代码/链接/图片），
     选区包裹与行首前缀都按光标位置来；贴图走附件接口，插入签名直链
   - 预览用 Markwon，图片用 Coil；正文落在一张白纸卡片里，不再贴屏幕边
   - 从任务详情与知识点都能进，保存按 `body_md` 回写（PATCH 带 version）

3. 表格
   - 只读渲染走 markdown-it 的 GFM 表，`display:block + overflow-x:auto`：
     宽表横向滚动、窄表铺满，都不撑破抽屉

验证：pytest 74 passed；richtext 15 / smoke 7 / tickets 8 / knowledge 7 全绿；
tsc -b 0 错；vite build 通过（主包 299.42 kB / gzip 74.96 kB）；
安卓 assembleDebug 成功并在 API 35 模拟器走通编辑与预览。

仍欠：保存后回列表而非回详情抽屉、图片压缩与缩略图、HTML 片段按文本显示。

android/app/src/main/java/com/dadao/task/MainActivity.kt

@@ -19,12 +19,15 @@ import androidx.compose.ui.platform.LocalContext
 import com.dadao.task.data.Api
 import com.dadao.task.data.TokenStore
 import com.dadao.task.data.Workspace
+import androidx.compose.foundation.layout.Box
 import com.dadao.task.ui.BoardScreen
 import com.dadao.task.ui.DadaoTheme
+import com.dadao.task.ui.EditRequest
 import com.dadao.task.ui.HomeScreen
 import com.dadao.task.ui.KnowledgeScreen
 import com.dadao.task.ui.LoginScreen
 import com.dadao.task.ui.MembersScreen
+import com.dadao.task.ui.RichTextEditorScreen
 import com.dadao.task.ui.TaskListScreen
 import com.dadao.task.ui.TicketsScreen
 import com.dadao.task.ui.WorkspaceScaffold
@@ -68,6 +71,8 @@ private fun AppRoot(joinUri: String?) {
     var current by remember { mutableStateOf<Workspace?>(null) }
     var tab by remember { mutableStateOf(WorkspaceTab.Tasks) }
     var unread by remember { mutableStateOf(0) }
+    // 打开富文本编辑器时非空；关掉就恢复原来的界面
+    var editing by remember { mutableStateOf<EditRequest?>(null) }
 
     // 有本地令牌就先静默校验一次：令牌过期/被吊销要退回登录页，而不是进了主页再崩。
     LaunchedEffect(screen) {
@@ -122,18 +127,62 @@ private fun AppRoot(joinUri: String?) {
             if (ws == null) {
                 screen = Screen.Home
             } else {
-                WorkspaceScaffold(
-                    workspace = ws,
-                    tab = tab,
-                    unread = unread,
-                    onTab = { tab = it },
-                    onBackHome = { screen = Screen.Home },
-                ) {
-                    when (tab) {
-                        WorkspaceTab.Tasks -> TaskListScreen(api = api, workspace = ws)
-                        WorkspaceTab.Tickets -> TicketsScreen(api = api, workspace = ws)
-                        WorkspaceTab.Knowledge -> KnowledgeScreen(api = api, workspace = ws)
-                        WorkspaceTab.Members -> MembersScreen(api = api, workspace = ws)
+                Box {
+                    WorkspaceScaffold(
+                        workspace = ws,
+                        tab = tab,
+                        unread = unread,
+                        onTab = { tab = it },
+                        onBackHome = { screen = Screen.Home },
+                    ) {
+                        when (tab) {
+                            WorkspaceTab.Tasks -> TaskListScreen(
+                                api = api,
+                                workspace = ws,
+                                onEdit = { editing = it },
+                            )
+
+                            WorkspaceTab.Tickets -> TicketsScreen(api = api, workspace = ws)
+                            WorkspaceTab.Knowledge -> KnowledgeScreen(
+                                api = api,
+                                workspace = ws,
+                                onEdit = { editing = it },
+                            )
+
+                            WorkspaceTab.Members -> MembersScreen(api = api, workspace = ws)
+                        }
+                    }
+
+                    val request = editing
+                    if (request != null) {
+                        RichTextEditorScreen(
+                            api = api,
+                            workspaceId = ws.id,
+                            itemId = request.itemId,
+                            initialTitle = request.title,
+                            initialBody = request.body,
+                            titleEnabled = request.titleEnabled,
+                            save = { title, body ->
+                                if (request.knowledge) {
+                                    api.updateKnowledge(
+                                        workspaceId = ws.id,
+                                        itemId = request.itemId,
+                                        version = request.version,
+                                        title = title,
+                                        body = body,
+                                    )
+                                } else {
+                                    api.updateItem(
+                                        workspaceId = ws.id,
+                                        itemId = request.itemId,
+                                        version = request.version,
+                                        title = title,
+                                        body = body,
+                                    )
+                                }
+                            },
+                            onClose = { editing = null },
+                        )
                     }
                 }
             }

android/app/src/main/java/com/dadao/task/data/Api.kt

@@ -10,6 +10,8 @@ import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonElement
 import okhttp3.MediaType.Companion.toMediaType
+import okhttp3.MediaType.Companion.toMediaTypeOrNull
+import okhttp3.MultipartBody
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import okhttp3.RequestBody.Companion.toRequestBody
@@ -136,8 +138,29 @@ data class ItemDetail(
     val tags: List<Tag> = emptyList(),
     val version: Int = 1,
     val activities: List<Activity> = emptyList(),
+    val attachments: List<Attachment> = emptyList(),
 )
 
+/**
+ * 附件。[rawUrl] 是后端签发的短时直链（带 exp/sig），
+ * 正文里的图片就用它，**不要**把长期凭据写进正文。
+ */
+@Serializable
+data class Attachment(
+    val id: String,
+    @SerialName("item_id") val itemId: String = "",
+    val filename: String = "",
+    @SerialName("content_type") val contentType: String = "application/octet-stream",
+    val size: Long = 0,
+    @SerialName("uploader_id") val uploaderId: String = "",
+    @SerialName("created_at") val createdAt: String = "",
+    @SerialName("raw_url") val rawUrl: String? = null,
+    @SerialName("can_delete") val canDelete: Boolean = false,
+)
+
+@Serializable
+data class AttachmentPage(val items: List<Attachment> = emptyList())
+
 @Serializable
 data class Invitation(
     val code: String,
@@ -223,6 +246,7 @@ data class KnowledgeDoc(
     val tags: List<Tag> = emptyList(),
     val knowledge: KnowledgeInfo = KnowledgeInfo(),
     val source: SourceRef? = null,
+    val attachments: List<Attachment> = emptyList(),
 )
 
 @Serializable
@@ -287,6 +311,13 @@ private data class KnowledgeCreateRequest(
 @Serializable
 private data class KnowledgeActionRequest(val action: String)
 
+@Serializable
+private data class ItemUpdateRequest(
+    val version: Int,
+    val title: String? = null,
+    @SerialName("body_md") val bodyMd: String? = null,
+)
+
 @Serializable
 private data class KnowledgeUpdateRequest(
     val version: Int,
@@ -451,6 +482,67 @@ class Api(private val tokens: TokenStore) {
         auth = true,
     )
 
+    // ---- 附件与富文本 ----
+
+    suspend fun attachments(workspaceId: String, itemId: String): List<Attachment> =
+        call<AttachmentPage>(
+            path = "/workspaces/$workspaceId/items/$itemId/attachments",
+            auth = true,
+        ).items
+
+    /**
+     * 上传附件。返回的 [Attachment.rawUrl] 是短时签名直链，
+     * 直接写进 Markdown 的 `![](...)` 即可，不需要把登录令牌塞进正文。
+     */
+    suspend fun uploadAttachment(
+        workspaceId: String,
+        itemId: String,
+        filename: String,
+        mimeType: String,
+        bytes: ByteArray,
+    ): Attachment = withContext(Dispatchers.IO) {
+        val form = MultipartBody.Builder()
+            .setType(MultipartBody.FORM)
+            .addFormDataPart(
+                "file",
+                filename,
+                bytes.toRequestBody(mimeType.toMediaTypeOrNull()),
+            )
+            .build()
+
+        val builder = Request.Builder()
+            .url("$base/workspaces/$workspaceId/items/$itemId/attachments")
+            .post(form)
+            .header("Accept", "application/json")
+        tokens.accessToken?.let { builder.header("Authorization", "Bearer $it") }
+
+        try {
+            http.newCall(builder.build()).execute().use { response ->
+                val text = response.body?.string().orEmpty()
+                val envelope = runCatching { json.decodeFromString<Envelope<Attachment>>(text) }
+                    .getOrElse { throw ApiException(1500, "上传失败（HTTP ${response.code}）") }
+                if (envelope.code != 0) throw ApiException(envelope.code, envelope.message, envelope.requestId)
+                envelope.data ?: throw ApiException(1500, "上传响应缺少 data")
+            }
+        } catch (e: IOException) {
+            throw unreachable(e)
+        }
+    }
+
+    /** 保存正文/标题。PATCH 必须带 version，冲突由服务端返回 4009。 */
+    suspend fun updateItem(
+        workspaceId: String,
+        itemId: String,
+        version: Int,
+        title: String? = null,
+        body: String? = null,
+    ): ItemDetail = call(
+        path = "/workspaces/$workspaceId/items/$itemId",
+        body = json.encodeToString(ItemUpdateRequest(version, title, body)),
+        auth = true,
+        method = "PATCH",
+    )
+
     // ---- M2 工单 ----
 
     /** role: assigned（派给我的）/ requested（我发起的）/ all。 */

android/app/src/main/java/com/dadao/task/ui/KnowledgeScreen.kt

@@ -55,7 +55,7 @@ private fun docTypeLabel(type: String): String = when (type) {
 }
 
 @Composable
-fun KnowledgeScreen(api: Api, workspace: Workspace) {
+fun KnowledgeScreen(api: Api, workspace: Workspace, onEdit: (EditRequest) -> Unit = {}) {
     val scope = rememberCoroutineScope()
     var tab by remember { mutableStateOf("draft") }
     var docs by remember { mutableStateOf<List<KnowledgeDoc>>(emptyList()) }
@@ -168,6 +168,7 @@ fun KnowledgeScreen(api: Api, workspace: Workspace) {
             workspace = workspace,
             doc = target,
             onClose = { open = null },
+            onEdit = onEdit,
             onChanged = {
                 scope.launch { reload() }
             },
@@ -249,6 +250,7 @@ private fun KnowledgeDetailDialog(
     onClose: () -> Unit,
     onChanged: () -> Unit,
     onFail: (Throwable) -> Unit,
+    onEdit: (EditRequest) -> Unit,
 ) {
     val scope = rememberCoroutineScope()
     var action by remember { mutableStateOf(doc.status) }
@@ -288,6 +290,21 @@ private fun KnowledgeDetailDialog(
         },
         confirmButton = {
             Row(horizontalArrangement = Arrangement.spacedBy(6.dp)) {
+                TextButton(
+                    onClick = {
+                        onEdit(
+                            EditRequest(
+                                itemId = doc.id,
+                                title = doc.title,
+                                body = doc.bodyMd,
+                                version = doc.version,
+                                titleEnabled = action == "draft",
+                                knowledge = true,
+                            ),
+                        )
+                        onClose()
+                    },
+                ) { Text("编辑正文") }
                 actions.forEach { (key, label) ->
                     TextButton(onClick = {
                         scope.launch {

android/app/src/main/java/com/dadao/task/ui/RichTextEditorScreen.kt

@@ -0,0 +1,428 @@
+package com.dadao.task.ui
+
+import android.content.Context
+import android.net.Uri
+import android.provider.OpenableColumns
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.horizontalScroll
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.navigationBarsPadding
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.statusBarsPadding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.text.BasicTextField
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.SolidColor
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.TextRange
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.font.FontStyle
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.input.TextFieldValue
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.compose.ui.viewinterop.AndroidView
+import coil.compose.AsyncImage
+import com.dadao.task.data.Api
+import com.dadao.task.data.ApiException
+import com.dadao.task.data.Attachment
+import io.noties.markwon.Markwon
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+
+/** 打开编辑器需要的最小上下文：改的是哪条、改前是什么。 */
+data class EditRequest(
+    val itemId: String,
+    val title: String,
+    val body: String,
+    val version: Int,
+    val titleEnabled: Boolean = true,
+    val knowledge: Boolean = false,
+)
+
+/**
+ * 富文本编辑器（Markdown 存储）。
+ *
+ * 为什么存 Markdown 而不是 HTML：任务备注、工单说明、知识正文都要能被检索、
+ * 被 LLM 读、被导出；HTML 里混着行内样式，清洗成本远高于收益。
+ * 因此编辑区写 Markdown，预览用 Markwon 渲染，图片传附件后用签名直链插入。
+ */
+@Composable
+fun RichTextEditorScreen(
+    api: Api,
+    workspaceId: String,
+    itemId: String,
+    initialTitle: String,
+    initialBody: String,
+    /** 保存动作由调用方决定：事项走 PATCH /items，知识走 PATCH /knowledge。 */
+    save: suspend (title: String?, body: String) -> Unit,
+    titleEnabled: Boolean = true,
+    onClose: (saved: Boolean) -> Unit,
+) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+
+    var title by remember { mutableStateOf(initialTitle) }
+    var field by remember { mutableStateOf(TextFieldValue(initialBody)) }
+    var preview by remember { mutableStateOf(false) }
+    var saving by remember { mutableStateOf(false) }
+    var error by remember { mutableStateOf<String?>(null) }
+    var images by remember { mutableStateOf(emptyList<Attachment>()) }
+
+    // 传过的图片：进来先拉一份，预览区与「图片」栏都用它
+    LaunchedEffect(itemId) {
+        runCatching { api.attachments(workspaceId, itemId) }
+            .onSuccess { images = it.filter { row -> row.contentType.startsWith("image/") } }
+    }
+
+    val picker = rememberLauncherForActivityResult(ActivityResultContracts.GetContent()) { uri ->
+        if (uri == null) return@rememberLauncherForActivityResult
+        scope.launch {
+            saving = true
+            try {
+                val bytes = withContext(Dispatchers.IO) {
+                    context.contentResolver.openInputStream(uri)?.use { it.readBytes() }
+                }
+                if (bytes == null) {
+                    error = "读不到这张图片，换个来源试试"
+                    return@launch
+                }
+                val name = displayName(context, uri) ?: "image-${System.currentTimeMillis()}.png"
+                val mime = context.contentResolver.getType(uri) ?: "image/png"
+                val created = api.uploadAttachment(workspaceId, itemId, name, mime, bytes)
+                images = images + created
+                // 插入用签名直链：它会过期，所以库里存的是干净的相对路径
+                field = insert(field, "![${created.filename}](${created.rawUrl.orEmpty()})\n")
+            } catch (e: ApiException) {
+                error = e.message
+            } catch (e: Exception) {
+                error = "上传失败：${e.message ?: "未知错误"}"
+            } finally {
+                saving = false
+            }
+        }
+    }
+
+    Column(
+        Modifier
+            .fillMaxSize()
+            .background(Paper)
+            .statusBarsPadding(),
+    ) {
+        // 顶部：取消 / 状态 / 预览 / 保存
+        Row(
+            Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 12.dp, vertical = 8.dp),
+            verticalAlignment = Alignment.CenterVertically,
+        ) {
+            GhostButton("取消", onClick = { onClose(false) })
+            Spacer(Modifier.width(10.dp))
+            Column(Modifier.weight(1f)) {
+                Text(
+                    if (preview) "预览" else "编辑",
+                    fontSize = 15.sp,
+                    fontWeight = FontWeight.SemiBold,
+                    color = Ink,
+                )
+                Text(
+                    "${field.text.length} 字 · Markdown",
+                    fontSize = 11.sp,
+                    color = InkMuted,
+                )
+            }
+            if (saving) {
+                CircularProgressIndicator(Modifier.size(16.dp), strokeWidth = 2.dp, color = Primary)
+                Spacer(Modifier.width(8.dp))
+            }
+            PrimaryButton(if (preview) "继续写" else "预览", onClick = { preview = !preview })
+            Spacer(Modifier.width(8.dp))
+            PrimaryButton(
+                "保存",
+                enabled = !saving,
+                onClick = {
+                    scope.launch {
+                        saving = true
+                        error = null
+                        try {
+                            save(if (titleEnabled) title else null, field.text)
+                            onClose(true)
+                        } catch (e: ApiException) {
+                            error = if (e.code == 4009) "刚被别人改过，请退出重进再改一次" else e.message
+                        } catch (e: Exception) {
+                            error = e.message ?: "保存失败"
+                        } finally {
+                            saving = false
+                        }
+                    }
+                },
+            )
+        }
+        HorizontalDivider(color = Line)
+
+        error?.let {
+            Text(
+                it,
+                color = Rust,
+                fontSize = 13.sp,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .background(RustSoft)
+                    .padding(horizontal = 14.dp, vertical = 8.dp),
+            )
+        }
+
+        // 编辑区做成一张纸：标题、工具栏、正文在同一张纸上，边界清楚
+        Box(
+            Modifier
+                .fillMaxSize()
+                .padding(horizontal = 12.dp, vertical = 10.dp),
+        ) {
+            Column(
+                Modifier
+                    .fillMaxSize()
+                    .clip(RoundedCornerShape(14.dp))
+                    .background(Color.White)
+                    .border(1.dp, Line, RoundedCornerShape(14.dp)),
+            ) {
+                if (titleEnabled) {
+                    BasicTextField(
+                        value = title,
+                        onValueChange = { title = it },
+                        singleLine = true,
+                        textStyle = TextStyle(
+                            fontSize = 19.sp,
+                            fontWeight = FontWeight.Bold,
+                            color = Ink,
+                        ),
+                        cursorBrush = SolidColor(Primary),
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(horizontal = 14.dp, vertical = 12.dp),
+                        decorationBox = { inner ->
+                            if (title.isBlank()) Text("标题", fontSize = 19.sp, color = InkMuted)
+                            inner()
+                        },
+                    )
+                    HorizontalDivider(color = Line)
+                } else if (preview) {
+                    Text(
+                        title.ifBlank { initialTitle },
+                        fontSize = 19.sp,
+                        fontWeight = FontWeight.Bold,
+                        color = Ink,
+                        modifier = Modifier.padding(horizontal = 14.dp, vertical = 12.dp),
+                    )
+                    HorizontalDivider(color = Line)
+                }
+
+                if (preview) {
+                    PreviewBody(field.text, images, Modifier.weight(1f))
+                } else {
+                    Row(
+                        Modifier
+                            .fillMaxWidth()
+                            .horizontalScroll(rememberScrollState())
+                            .padding(horizontal = 10.dp, vertical = 6.dp),
+                        horizontalArrangement = Arrangement.spacedBy(6.dp),
+                        verticalAlignment = Alignment.CenterVertically,
+                    ) {
+                        ToolButton("B", bold = true) { field = wrap(field, "**") }
+                        ToolButton("I", italic = true) { field = wrap(field, "*") }
+                        ToolButton("标题") { field = prefixLines(field, "## ") }
+                        ToolButton("列表") { field = prefixLines(field, "- ") }
+                        ToolButton("引用") { field = prefixLines(field, "> ") }
+                        ToolButton("代码") { field = wrap(field, "`") }
+                        ToolButton("链接") { field = insert(field, "[文字](https://)") }
+                        ToolButton("图片") { picker.launch("image/*") }
+                    }
+                    HorizontalDivider(color = Line)
+
+                    Box(
+                        Modifier
+                            .fillMaxSize()
+                            .padding(horizontal = 14.dp, vertical = 12.dp),
+                    ) {
+                        BasicTextField(
+                            value = field,
+                            onValueChange = { field = it },
+                            textStyle = TextStyle(fontSize = 15.sp, color = Ink, lineHeight = 24.sp),
+                            cursorBrush = SolidColor(Primary),
+                            modifier = Modifier
+                                .fillMaxSize()
+                                .navigationBarsPadding(),
+                            decorationBox = { inner ->
+                                if (field.text.isBlank()) {
+                                    Text(
+                                        "写点什么。「B」「列表」在光标处插语法，图片直接选会自动上传。",
+                                        fontSize = 15.sp,
+                                        color = InkMuted,
+                                        lineHeight = 24.sp,
+                                    )
+                                }
+                                inner()
+                            },
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+@Composable
+private fun PreviewBody(
+    source: String,
+    images: List<Attachment>,
+    modifier: Modifier = Modifier,
+) {
+    val context = LocalContext.current
+    val markwon = remember { Markwon.create(context) }
+    val text = remember(source) {
+        // 预览里图片单独排一栏（Markwon 核心版不联网取图），正文里的图片语法换成占位说明
+        source.replace(Regex("!\\[[^\\]]*\\]\\([^)]*\\)"), "〔图片〕")
+    }
+
+    Column(
+        modifier
+            .fillMaxWidth()
+            .verticalScroll(rememberScrollState())
+            .padding(horizontal = 14.dp, vertical = 12.dp)
+            .navigationBarsPadding(),
+    ) {
+        if (images.isNotEmpty()) {
+            Row(
+                Modifier
+                    .fillMaxWidth()
+                    .horizontalScroll(rememberScrollState()),
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                images.forEach { image ->
+                    AsyncImage(
+                        model = image.rawUrl,
+                        contentDescription = image.filename,
+                        modifier = Modifier
+                            .size(96.dp)
+                            .clip(RoundedCornerShape(10.dp)),
+                    )
+                }
+            }
+            Spacer(Modifier.height(12.dp))
+        }
+
+        if (text.isBlank()) {
+            Text("还没有内容", fontSize = 14.sp, color = InkMuted)
+        } else {
+            AndroidView(
+                factory = { ctx ->
+                    android.widget.TextView(ctx).apply {
+                        setTextIsSelectable(true)
+                        textSize = 15f
+                        setPadding(0, 0, 0, 0)
+                        setLineSpacing(0f, 1.5f)
+                        setTextColor(android.graphics.Color.parseColor("#4A5854"))
+                        markwon.setMarkdown(this, text)
+                    }
+                },
+                update = { view -> markwon.setMarkdown(view, text) },
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .heightIn(min = 120.dp),
+            )
+        }
+    }
+}
+
+/** 工具条按钮：小、方、无多余留白，横滑容得下。 */
+@Composable
+private fun ToolButton(
+    label: String,
+    bold: Boolean = false,
+    italic: Boolean = false,
+    onClick: () -> Unit,
+) {
+    Box(
+        Modifier
+            .clip(RoundedCornerShape(8.dp))
+            .background(PaperSunken)
+            .clickable { onClick() }
+            .padding(horizontal = 10.dp, vertical = 6.dp),
+    ) {
+        Text(
+            label,
+            fontSize = 13.sp,
+            color = InkSoft,
+            fontWeight = if (bold) FontWeight.Bold else FontWeight.Medium,
+            fontStyle = if (italic) FontStyle.Italic else null,
+        )
+    }
+}
+
+/** 把选区包起来：没选就插一对并落光标在中间，选了就把选中的包进去。 */
+private fun wrap(field: TextFieldValue, token: String): TextFieldValue {
+    val start = field.selection.start.coerceIn(0, field.text.length)
+    val end = field.selection.end.coerceIn(start, field.text.length)
+    val picked = field.text.substring(start, end)
+    val next = field.text.substring(0, start) + token + picked + token + field.text.substring(end)
+    val caret = if (picked.isEmpty()) start + token.length else start + picked.length + token.length * 2
+    return field.copy(text = next, selection = TextRange(caret))
+}
+
+/** 行首插前缀（标题/列表/引用），一次处理选区覆盖的每一行。 */
+private fun prefixLines(field: TextFieldValue, prefix: String): TextFieldValue {
+    val start = field.selection.start.coerceIn(0, field.text.length)
+    val end = field.selection.end.coerceIn(start, field.text.length)
+    val lineStart = field.text.lastIndexOf('\n', (start - 1).coerceAtLeast(0)).let {
+        if (it < 0 || start == 0) 0 else it + 1
+    }
+    val before = field.text.substring(0, lineStart)
+    val block = field.text.substring(lineStart, end)
+    val after = field.text.substring(end)
+    val nextBlock = block.split('\n').joinToString("\n") { line ->
+        if (line.startsWith(prefix)) line else prefix + line
+    }
+    val next = before + nextBlock + after
+    return field.copy(text = next, selection = TextRange(lineStart + nextBlock.length))
+}
+
+private fun insert(field: TextFieldValue, snippet: String): TextFieldValue {
+    val start = field.selection.start.coerceIn(0, field.text.length)
+    val end = field.selection.end.coerceIn(start, field.text.length)
+    val next = field.text.substring(0, start) + snippet + field.text.substring(end)
+    return field.copy(text = next, selection = TextRange(start + snippet.length))
+}
+
+private fun displayName(context: Context, uri: Uri): String? = runCatching {
+    context.contentResolver.query(uri, arrayOf(OpenableColumns.DISPLAY_NAME), null, null, null)
+        ?.use { cursor -> if (cursor.moveToFirst()) cursor.getString(0) else null }
+}.getOrNull()

android/app/src/main/java/com/dadao/task/ui/TaskDetailSheet.kt

@@ -66,6 +66,8 @@ fun TaskDetailSheet(
     itemId: String,
     onClose: () -> Unit,
     onChanged: () -> Unit,
+    /** 进富文本编辑器改正文。标题与状态留在抽屉里，只有正文要更大地方。 */
+    onEdit: (ItemDetail) -> Unit = {},
 ) {
     val sheet = rememberModalBottomSheetState(skipPartiallyExpanded = true)
     val scope = rememberCoroutineScope()
@@ -125,6 +127,8 @@ fun TaskDetailSheet(
                         )
                         Spacer(Modifier.width(6.dp))
                         if (d.kind == "ticket") SoftPill("工单", Clay, ClaySoft)
+                        Spacer(Modifier.weight(1f))
+                        GhostButton("编辑正文", onClick = { onEdit(d) })
                     }
                     Spacer(Modifier.height(8.dp))
                     OutlinedTextField(

android/app/src/main/java/com/dadao/task/ui/TaskListScreen.kt

@@ -51,7 +51,7 @@ private val views = listOf(
 )
 
 @Composable
-fun TaskListScreen(api: Api, workspace: Workspace) {
+fun TaskListScreen(api: Api, workspace: Workspace, onEdit: (EditRequest) -> Unit = {}) {
     val scope = rememberCoroutineScope()
     var view by remember { mutableStateOf("active") }
     var mode by remember { mutableStateOf("list") }
@@ -193,6 +193,10 @@ fun TaskListScreen(api: Api, workspace: Workspace) {
             itemId = id,
             onClose = { openId = null },
             onChanged = { scope.launch { reload() } },
+            onEdit = {
+                openId = null
+                onEdit(EditRequest(it.id, it.title, it.bodyMd, it.version))
+            },
         )
     }
 }