支持消息 Markdown 与欢迎语富文本

聊天/离线提示使用 Markdown 安全渲染；欢迎语改为 TipTap 富文本（颜色字号），DOMPurify 白名单清洗后展示。

web/src/pages/agent/Dashboard.tsx

@@ -7,6 +7,7 @@ import {
 } from '@ant-design/icons'
 import EmojiPicker, { insertAtCursor } from '@/components/common/EmojiPicker'
 import { ChatImage } from '@/components/common/ImagePreview'
+import MarkdownBody, { stripMarkdown } from '@/components/common/MarkdownBody'
 import { useAuth } from '@/stores/auth'
 import {
   addSessionNote, claimSession, endSession, getAvailableAgents, getCustomers, getKnowledgeEntries,
@@ -327,7 +328,7 @@ const Dashboard = () => {
         cursor = lastBatchSeq
       }
       if (latest && selectedIdRef.current === id) {
-        const preview = latest.type === 'image' ? '[图片]' : latest.content
+        const preview = latest.type === 'image' ? '[图片]' : stripMarkdown(latest.content)
         setSessions(previous => previous.map(session =>
           session.id === id
             ? {
@@ -360,7 +361,7 @@ const Dashboard = () => {
       return true
     }
 
-    const preview = msg.type === 'image' ? '[图片]' : msg.content
+    const preview = msg.type === 'image' ? '[图片]' : stripMarkdown(msg.content)
     let appended = false
     setDetail(previous => {
       if (selectedIdRef.current !== sessionId) return previous
@@ -1183,7 +1184,12 @@ const Dashboard = () => {
                             {message.type === 'image' ? (
                               <ChatImage src={message.content} alt="聊天图片" className="max-w-64 max-h-64" />
                             ) : (
-                              <p className="text-sm leading-normal whitespace-pre-wrap break-words m-0">{message.content}</p>
+                              <MarkdownBody
+                                tone={isAgent ? 'inverse' : 'default'}
+                                className="text-sm"
+                              >
+                                {message.content}
+                              </MarkdownBody>
                             )}
                           </div>
                           <div className={`mt-1 text-xs text-neutral-400 ${isAgent ? 'text-right' : ''}`}>
@@ -1289,7 +1295,7 @@ const Dashboard = () => {
                       ref={messageInputRef}
                       rows={3}
                       className="flex-1 min-w-0 min-h-[88px] max-h-[160px] rounded-xl px-3.5 py-3 bg-neutral-50 border border-neutral-200 text-sm leading-6 text-neutral-800 placeholder:text-neutral-400 outline-none resize-y focus:border-[#2563eb] transition-colors"
-                      placeholder="输入回复内容… / 调话术，Enter 发送，Shift+Enter 换行"
+                      placeholder="支持 Markdown（**加粗** *斜体* 列表 链接）… / 调话术，Enter 发送"
                       value={messageInput}
                       onChange={event => {
                         const v = event.target.value