feat(web): 前端 P0 收尾（多路忙态收口 / 握手 history 落 store / 清理幽灵键）

frontend/web/src/store/useAppStore.ts

@@ -18,6 +18,7 @@ import { now, uid } from "../lib/util";
 import {
   currentGraph,
   dropMessage,
+  mergeHistory,
   mergeMessage,
   patchAssistantTail,
   patchMessage,
@@ -144,6 +145,13 @@ export interface AppStore extends TurnSlice {
    *  renders twice (design/16 §4.3 dedup). A message without a session id (a local
    *  optimistic bubble) belongs to the active session. */
   appendOrUpdateMessage: (msg: ChatMessage) => void;
+  /** Merge one handshake `history` replay page (contract §3.2) into the session the
+   *  frame names — up to 50 already-persisted rows, once per (re)connect. Dedup by
+   *  id and adopt a local optimistic bubble only on an exact key (`clientMsgId` for
+   *  users / `turnId` for assistants), never by the content/time heuristic: this is
+   *  the reconnect catch-up path, so a wrong adopt would rewrite a streaming bubble
+   *  with an old reply. */
+  mergeHistoryPage: (sessionId: string, msgs: ChatMessage[]) => void;
   /** Patch one already-rendered message in place by id — the `message_edited` WS
    *  path. With `sessionId` the patch is confined to that session's bucket; without
    *  one the id is searched across the active list and every bucket (ids are
@@ -280,6 +288,14 @@ export const useAppStore = create<AppStore>()(
           )
         ),
 
+      mergeHistoryPage: (sessionId, list) =>
+        set((s) => {
+          if (!list.length) return s;
+          return writeSession(s, sessionId || s.activeSessionId, (cur) =>
+            mergeHistory(cur, list)
+          );
+        }),
+
       updateMessageById: (id, patch, sessionId) =>
         set((s) =>
           writeSessionById(s, sessionId, (list) => patchMessage(list, id, patch))