feat(mcp): 增强MCP服务器异常处理和错误描述

- 添加_iter_leaf_exceptions函数用于处理嵌套异常组
- 实现_describe_mcp_exception函数提供详细的MCP服务器错误信息
- 改进connect_mcp_servers中的错误处理，使用更精确的错误描述
- 在日志记录中包含更具体的错误详情

feat(outlook): 优化Outlook集成异常处理

- 添加_iter_leaf_exceptions函数用于异常处理
- 创建_coerce_outlook_mcp_exception函数统一异常转换
- 改进_call_outlook_mcp_tool中的异常捕获和处理
- 对认证令牌获取和MCP调用添加专门的超时和HTTP错误处理

feat(web): 改进Web会话定时任务结果记录

- 实现_record_cron_result_for_web_session函数
- 为Web模式下的独立定时任务执行结果提供持久化存储
- 支持将定时任务响应消息添加到目标会话中
- 确保前端可以显示定时任务执行结果

app-instance/backend/nanobot/web/server.py

@@ -540,6 +540,40 @@ def _infer_cron_route_from_session_key(session_key: str | None) -> tuple[str | N
     return channel, chat_id
 
 
+def _record_cron_result_for_web_session(
+    *,
+    session_manager: SessionManager,
+    job: CronJob,
+    result: CronExecutionResult,
+) -> str | None:
+    """Persist standalone web cron output so the frontend can surface it."""
+    target_session_key = _resolve_cron_session_key(job)
+    if not target_session_key.startswith("web:"):
+        return None
+
+    # agent_turn jobs already write their own history via AgentLoop.process_direct().
+    if job.payload.kind == "agent_turn":
+        return target_session_key
+
+    # reminder/system_event jobs bypass the agent loop, so standalone web mode
+    # must append the final message into the target session explicitly.
+    if job.payload.kind != "system_event" or not job.payload.deliver or not result.response:
+        return None
+
+    session = session_manager.get_or_create(target_session_key)
+    session.add_message(
+        "assistant",
+        result.response,
+        metadata={
+            "source": "cron",
+            "job_id": job.id,
+            "job_name": job.name,
+        },
+    )
+    session_manager.save(session)
+    return target_session_key
+
+
 # ============================================================================
 # App factory
 # ============================================================================
@@ -635,8 +669,12 @@ def create_app(
                 default_channel="web",
                 default_chat_id="default",
             )
-            target_session_key = _resolve_cron_session_key(job)
-            if job.payload.kind == "agent_turn" and target_session_key.startswith("web:"):
+            target_session_key = _record_cron_result_for_web_session(
+                session_manager=session_manager,
+                job=job,
+                result=result,
+            )
+            if target_session_key:
                 await websocket_broadcaster.broadcast({
                     "type": "session_updated",
                     "session_id": target_session_key,