chat: 持久化继续消息，chat-history 交替历史

基线 main 811912c（PR #125 Muse 风格之后）：服务端与单测与
9538825 相同；React 侧在 Muse 风格 ContinuePanel 上重放
chat-history 集成（新版输入框占位文案保持 Muse 风格的“消息”），
console.html 由新版 src 重新构建。

- 新表 task_continue_messages：POST /continue 的用户消息与状态改回
  queued 同一事务落盘，409 被拒不留 phantom 消息
- GET /tasks/{id}/chat-history：prompt + 继续 + 后续消息 + 链路按
  时间交错拼好返回；部署前继续以 legacy_continue_count 如实标注
- React ContinuePanel 优先用 chat-history，旧服务端自动回退

cloud/console-react/src/sections/detail/ContinuePanel.tsx

@@ -5,25 +5,33 @@ import { traceEntryToChatMessage, type ChatMessage } from "../../components/chat
 import { TRACE_TERMINAL } from "../../api/types";
 
 // Continue chat: same ChatList/ChatBubble/ChatInput as the trace timeline.
-// History is the task prompt (user) + message-kind trace entries
-// (assistant) + followups already sent (user). Live followups and trace
-// entries carry no timestamps, so they cannot be interleaved exactly:
-// followups are appended after trace messages and this is stated here
-// and in the final report, not hidden by a fabricated order.
-// Sending uses only live APIs: terminal tasks -> POST /tasks/:id/continue,
-// queued/running tasks -> POST /tasks/:id/followups (direct). No new API.
+// Preferred source is GET /chat-history (server-merged true alternating
+// history: prompt + persisted continues + followups + trace, in
+// timestamp order). Only when that endpoint is unavailable (old server)
+// fall back to the previous view: prompt + message-kind trace entries
+// + followups appended after — that fallback cannot interleave exactly
+// and cannot show pre-persistence continues, and it says so nowhere
+// else, so the fallback path is kept only as a compatibility shim.
+// Sending uses only live APIs: terminal tasks -> POST /tasks/:id/continue
+// (the server now persists that message in the same transaction),
+// queued/running tasks -> POST /tasks/:id/followups (direct).
 export default function ContinuePanel() {
   const ctx = useConsole();
   const t = ctx.currentTask;
   const messages = useMemo<ChatMessage[]>(() => {
     if (!t) return [];
+    if (ctx.chatHistory) {
+      return ctx.chatHistory.messages.map((m) => ({
+        id: m.id, role: m.role, text: m.text, label: m.label,
+      }));
+    }
     const head: ChatMessage[] = t.prompt ? [{ id: "task-prompt", role: "user", text: t.prompt }] : [];
     const assistant = ctx.traceEntries.filter((e) => e.kind === "message").map((e, i) => traceEntryToChatMessage(e, i));
     const followups: ChatMessage[] = ctx.followups.map((f, i) => ({
       id: "followup-" + i, role: "user" as const, text: String(f.body || ""), label: "后续消息",
     }));
     return [...head, ...assistant, ...followups];
-  }, [t, ctx.traceEntries, ctx.followups]);
+  }, [t, ctx.chatHistory, ctx.traceEntries, ctx.followups]);
   if (!t) return <div className="muted">点任务行查看详情后，这里显示继续会话</div>;
   const terminal = TRACE_TERMINAL.includes(t.status);
   const running = ["queued", "running"].includes(t.status);
@@ -33,8 +41,15 @@ export default function ContinuePanel() {
     : running
       ? "运行中/排队中：发送走后续消息直接发送（跑完当前轮后优先执行）"
       : "merged/merge-failed 任务不可继续，也不可发后续消息";
+  const legacy = ctx.chatHistory ? (ctx.chatHistory.legacy_continue_count ?? null) : null;
   return (
     <div className="chat-column">
+      {legacy !== null && legacy > 0 ? (
+        <div className="muted">此前有 {legacy} 条继续消息发生在持久化之前，未入库，上面历史不完整；部署后新发的继续消息会正常显示。</div>
+      ) : null}
+      {ctx.chatHistory && ctx.chatHistory.trace_note ? (
+        <div className="muted">{ctx.chatHistory.trace_note}</div>
+      ) : null}
       <ChatList messages={messages} empty="（暂无会话消息）" />
       <ChatInput
         disabled={!canSend}