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/api/paths.ts

@@ -38,6 +38,7 @@ export const paths = {
   taskApprovals: (id: string) => "/tasks/" + enc(id) + "/approvals",
   taskApprovalDecision: (id: string, aid: string, verb: string) => "/tasks/" + enc(id) + "/approvals/" + enc(aid) + "/" + verb,
   taskFollowups: (id: string) => "/tasks/" + enc(id) + "/followups",
+  taskChatHistory: (id: string) => "/tasks/" + enc(id) + "/chat-history",
   taskMessages: (id: string) => "/tasks/" + enc(id) + "/messages",
   taskMessagesTo: (target: string) => "/tasks/" + enc(target) + "/messages",
   taskThread: (id: string) => "/tasks/" + enc(id) + "/thread",