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/context.ts

@@ -1,5 +1,5 @@
 import { createContext, useContext } from "react";
-import type { Automation, Env, Member, Project, Review, Approval, Followup, PeerMessage, Task, ThreadInfo, Triage, Worker, SkillItem, McpServer, Agent, DispatchBody, ReviewBody, TraceEntry } from "./api/types";
+import type { Automation, Env, Member, Project, Review, Approval, Followup, PeerMessage, Task, ThreadInfo, Triage, Worker, SkillItem, McpServer, Agent, DispatchBody, ReviewBody, TraceEntry, ChatHistory } from "./api/types";
 
 export interface ConsoleCtx {
   keySaved: boolean; keyState: string;
@@ -30,6 +30,7 @@ export interface ConsoleCtx {
   reviews: Review[]; reviewMsg: string; reviewError: string; refreshReviews: () => void; postReview: (body: ReviewBody) => Promise<void>; submitFindings: (id: string) => void;
   traceEntries: TraceEntry[]; traceNote: string; traceDone: string; traceKind: string; setTraceKind: (v: string) => void; downloadTrace: () => void; traceMsg: string;
   sendChatMessage: (text: string) => Promise<void>; chatMsg: string;
+  chatHistory: ChatHistory | null;
   followups: Followup[];
   approvals: Approval[]; approvalMsg: string; refreshApprovals: () => void; decideApproval: (id: string, decision: string) => void;
   peerMessages: PeerMessage[]; peerMsg: string; postPeer: (mode: string, target: string, text: string) => Promise<void>;