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/hooks/useTaskDetail.ts

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 import { api, getKey } from "../api/client";
 import { paths } from "../api/paths";
 import { TRACE_TERMINAL } from "../api/types";
-import type { Agent, Approval, Followup, PeerMessage, Review, Task, ThreadInfo, TraceEntry } from "../api/types";
+import type { Agent, Approval, ChatHistory, Followup, PeerMessage, Review, Task, ThreadInfo, TraceEntry } from "../api/types";
 
 // Task detail state: the selected task, its trace SSE/one-shot stream,
 // and every structured sub-list. Chat sending lives here too:
@@ -36,6 +36,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
   const [threadMsg, setThreadMsg] = useState("");
   const [threadList, setThreadList] = useState<ThreadInfo[]>([]);
   const [chatMsg, setChatMsg] = useState("");
+  const [chatHistory, setChatHistory] = useState<ChatHistory | null>(null);
   const traceAbortRef = useRef<AbortController | null>(null);
   const agentTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const currentTaskRef = useRef<Task | null>(null);
@@ -72,6 +73,15 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
     catch { setFollowups([]); }
   }, []);
 
+  // True alternating history: server-merged prompt + persisted
+  // continues + followups + trace, in timestamp order. On failure
+  // (old server without /chat-history) keep null and ContinuePanel
+  // falls back to its previous prompt + trace + followups view.
+  const loadChatHistory = useCallback(async (taskId: string) => {
+    try { const d = await api<ChatHistory>(paths.taskChatHistory(taskId)); setChatHistory(d); }
+    catch { setChatHistory(null); }
+  }, []);
+
   const loadReviews = useCallback(async (taskId?: string) => {
     const id = taskId || currentTaskRef.current?.id;
     if (!id) return;
@@ -226,6 +236,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
       void startTrace(taskId, t.status);
       void loadAgents(taskId);
       void loadCoordChildren(t);
+      void loadChatHistory(taskId);
       void loadFollowups(taskId);
       void loadPeerMessages(taskId);
       void loadThread(taskId);
@@ -236,7 +247,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
       setCurrentTask(null);
       setDetailBody("加载失败：" + e.message);
     }
-  }, [stopTrace, startTrace, loadAgents, loadCoordChildren, loadFollowups, loadPeerMessages, loadThread, loadThreads, loadReviews, loadApprovals, getRole]);
+  }, [stopTrace, startTrace, loadAgents, loadCoordChildren, loadChatHistory, loadFollowups, loadPeerMessages, loadThread, loadThreads, loadReviews, loadApprovals, getRole]);
 
   const refreshDetailLists = useCallback(async () => {
     const t = currentTaskRef.current;
@@ -250,6 +261,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
       setDetailBody(body || "（暂无 result/error 输出）");
     } catch { /* light header refresh must not clear the detail */ }
     void loadFollowups(t.id);
+    void loadChatHistory(t.id);
     void loadReviews(t.id);
     void loadApprovals(t.id);
     void loadCoordChildren(t);
@@ -257,7 +269,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
     void loadPeerMessages(t.id);
     void loadThread(t.id);
     void loadThreads(t.id);
-  }, [loadFollowups, loadReviews, loadApprovals, loadCoordChildren, loadAgents, loadPeerMessages, loadThread, loadThreads]);
+  }, [loadFollowups, loadChatHistory, loadReviews, loadApprovals, loadCoordChildren, loadAgents, loadPeerMessages, loadThread, loadThreads]);
 
   const doAction = useCallback(async (kind: string) => {
     const t = currentTaskRef.current;
@@ -370,11 +382,12 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
         await api(paths.taskFollowups(t.id), "POST", { body: v, mode: "direct" });
         setChatMsg("已直接发送");
         await loadFollowups(t.id);
+        await loadChatHistory(t.id);
       } else {
         setChatMsg("merged/merge-failed 任务不可继续，也不可发后续消息");
       }
     } catch (e: any) { setChatMsg("发送失败：" + e.message); }
-  }, [showDetail, onTasksReload, loadFollowups]);
+  }, [showDetail, onTasksReload, loadFollowups, loadChatHistory]);
 
   const downloadTrace = useCallback(async () => {
     const t = currentTaskRef.current;
@@ -399,7 +412,7 @@ export function useTaskDetail(getRole: (pid?: string) => string | null, onTasksR
     currentTask, detailBody, actionMsg, actionReasons, costBox, forkVisible, setForkVisible, forkMsg,
     coordChildren, agents, agentsNote, reviews, reviewMsg, reviewError, traceEntries, traceNote, traceDone,
     traceKind, setTraceKind, traceMsg, followups, approvals, approvalMsg, peerMessages, peerMsg,
-    threadText, threadGateNote, threadMsg, threadList, chatMsg,
+    threadText, threadGateNote, threadMsg, threadList, chatMsg, chatHistory,
     showDetail, refreshDetailLists, doAction, taskCost, forkTask, postReview, submitFindings,
     decideApproval, postPeer, threadAction, sendChatMessage, downloadTrace,
     refreshReviews: () => void loadReviews(), refreshApprovals: () => void loadApprovals(),