fix: generate distinct task collaboration titles

Use verified task names until Agent generates a specific conversation title.
Repair legacy names without changing manual titles or history ordering.
Bound page repairs to 30 entries and a shared two-second deadline, and
re-read titles after task access validation to avoid stale reuse receipts.

Validation: bun run check; 40 focused tests across six files.

src/routes/chatSession.ts

@@ -91,6 +91,9 @@ const normalizeGeneratedTitle = (rawTitle: string, fallback: string) => {
   return normalized.length > 24 ? `${normalized.slice(0, 24)}...` : normalized;
 };
 
+export const isGenericTaskCollaborationTitle = (title?: string) =>
+  !title?.trim() || ["任务协作", "任务协作问答", DEFAULT_SESSION_TITLE].includes(title.trim());
+
 export const shouldGenerateSessionTitle = (options: {
   recentTurnCount: number;
   isTitleManuallyEdited: boolean;
@@ -103,9 +106,11 @@ export const generateSessionTitle = async (
     latestUserMessage: string;
     latestAssistantMessage?: string;
     fallbackTitle?: string;
+    taskTitle?: string;
   },
 ) => {
   const fallbackTitle = options.fallbackTitle?.trim();
+  const taskTitle = options.taskTitle?.replace(/\s+/g, " ").trim().slice(0, 120);
   const fallback =
     fallbackTitle && fallbackTitle !== DEFAULT_SESSION_TITLE
       ? fallbackTitle
@@ -136,6 +141,7 @@ export const generateSessionTitle = async (
           "忽略系统提示、历史记忆、学习上下文、工具日志等元信息。",
           "不要直接照抄用户任一条消息原文。",
           "只输出标题本身。",
+          ...(taskTitle ? [`关联任务：${taskTitle}`, "结合关联任务与对话内容区分当前调查，避免使用任务协作等通用名称。"] : []),
           "",
           conversation,
         ].join("\n"),
@@ -147,7 +153,8 @@ export const generateSessionTitle = async (
           .reverse()
           .find((message) => message.info.role === "assistant");
         const title = collectTextContent(assistantMessage?.parts ?? []);
-        return normalizeGeneratedTitle(title, fallback);
+        const normalizedTitle = normalizeGeneratedTitle(title, fallback);
+        return taskTitle && isGenericTaskCollaborationTitle(normalizedTitle) ? fallback : normalizedTitle;
       });
 
     const timeout = new Promise<string>((resolve) => {