fix: synchronize task collaboration session titles

Apply creation titles and repaired history names to cached sessions.
Keep messages and reading state intact and preserve title edits received
while a collaboration request is in flight.

Validation: pnpm lint; pnpm typecheck; 604 unit tests; two browser regressions.

tests/browser/investigation-main-chat.e2e.ts

@@ -102,6 +102,22 @@ test("单一协作入口展示任务引用，保留草稿且仅手动发送，
   await page.emulateMedia({ reducedMotion: "reduce" });
   await mockWorkbenchContext(page);
   await mockAgentApi(page, { sessions: [{ session_id: "ordinary-main", title: "供水核查主聊天", purpose: "ordinary_chat", created_at: now, updated_at: now }] });
+  let collaborationOpens = 0;
+  const renamedCollaborationTitle = "异味投诉现场复核记录";
+  let finishReopen!: () => void;
+  const reopenGate = new Promise<void>((resolve) => { finishReopen = resolve; });
+  await page.route(`**/task/${taskId}/collaboration/session`, async (route) => {
+    collaborationOpens += 1;
+    if (collaborationOpens === 2) await reopenGate;
+    return route.fulfill({ headers: { "Access-Control-Allow-Origin": "*" }, json: {
+      session_id: `collaboration-${taskId}`, purpose: "task_collaboration", task_id: taskId,
+      title: collaborationOpens <= 2 ? task.title : renamedCollaborationTitle,
+      created: collaborationOpens === 1, status: "active",
+    } });
+  });
+  await page.route(`**/session/collaboration-${taskId}/title`, (route) => route.fulfill({
+    headers: { "Access-Control-Allow-Origin": "*" }, json: { id: `collaboration-${taskId}`, title: route.request().postDataJSON().title },
+  }));
   let submitted = 0;
   let inboxReads = 0;
   let incoming = false;
@@ -146,7 +162,7 @@ test("单一协作入口展示任务引用，保留草稿且仅手动发送，
   await expect(feed.getByRole("button", { name: "Agent 协作", exact: true })).toHaveAttribute("title", "打开调查协作对话，引用此任务，不会直接发送。");
   await feed.screenshot({ path: testInfo.outputPath("investigation-entry-desktop.png") });
   await feed.getByRole("button", { name: "Agent 协作", exact: true }).click();
-  await expect(agent.getByText("任务协作问答", { exact: true }).first()).toBeVisible();
+  await expect(agent.locator(".agent-chat-context-bar > p")).toHaveText(task.title);
   const reference = agent.getByRole("group", { name: "对话引用" });
   await expect(reference).toContainText("居民异味投诉调查");
   await expect(reference).toContainText("第 1 轮 · 报告第 3 版");
@@ -156,6 +172,18 @@ test("单一协作入口展示任务引用，保留草稿且仅手动发送，
   await expect(prompt).toBeFocused();
   expect(submitted).toBe(0);
   await feed.getByRole("button", { name: "Agent 协作", exact: true }).click();
+  await expect.poll(() => collaborationOpens).toBe(2);
+  await agent.getByRole("button", { name: "打开 Agent 历史记录" }).click();
+  const renameDialog = page.getByRole("dialog", { name: "历史对话" });
+  await renameDialog.getByRole("button", { name: `会话操作：${task.title}` }).click();
+  await page.getByRole("menuitem", { name: "重命名对话", exact: true }).click();
+  await renameDialog.getByRole("textbox", { name: "会话标题", exact: true }).fill(renamedCollaborationTitle);
+  await renameDialog.getByRole("button", { name: "保存对话标题" }).click();
+  await expect(renameDialog.locator("button.agent-history-session-trigger").filter({ hasText: renamedCollaborationTitle })).toBeVisible();
+  await page.keyboard.press("Escape");
+  finishReopen();
+  await expect(prompt).toBeFocused();
+  await expect(agent.locator(".agent-chat-context-bar > p")).toHaveText(renamedCollaborationTitle);
   await expect(prompt).toBeFocused();
   await expect(prompt).toHaveValue("保留的现场补充草稿");
   await feed.getByLabel("主要依据").getByRole("button", { name: "围绕此证据提问" }).click();
@@ -200,6 +228,7 @@ test("单一协作入口展示任务引用，保留草稿且仅手动发送，
   await expect(mobileAgent.getByRole("button", { name: "停止 Agent 分析" })).toHaveCount(0);
   incoming = true;
   await mobileAgent.getByRole("button", { name: "打开 Agent 历史记录" }).click();
+  await expect(page.getByRole("dialog", { name: "历史对话" }).locator("button.agent-history-session-trigger").filter({ hasText: renamedCollaborationTitle })).toBeVisible();
   await page.getByRole("dialog", { name: "历史对话" }).getByRole("button", { name: /^供水核查主聊天/ }).click();
   await expect(mobileAgent.getByRole("group", { name: "对话引用" })).toHaveCount(0);
   await expect(mobileAgent.getByText("已核对上游监测，请补充现场采样记录。")).toBeVisible();