feat(steward): off_topic 场景细分与引导回复

- 将业务无关输入细分为 greeting / meaningless / off_business 三类场景
- 新增 StewardOffTopicAgent，用 function calling 生成管家语气引导回复
- steward endpoint 与 user_agent_application 串联 off_topic 引导话术
- 补充 planner 与 user agent 的 off_topic 覆盖测试

server/tests/test_user_agent_service.py

@@ -753,6 +753,33 @@ def test_user_agent_application_submit_blocks_overlapping_travel_dates() -> None
         assert response.draft_payload is None
 
 
+def test_user_agent_application_maps_preview_travel_type_label() -> None:
+    session_factory = build_session_factory()
+    with session_factory() as db:
+        response = build_application_user_agent_response(
+            db,
+            "申请出差，2月20-23日上海，火车",
+            context_overrides={
+                "name": "曹笑竹",
+                "department_name": "技术部",
+                "grade": "P5",
+                "application_preview": {
+                    "fields": {
+                        "applicationType": "travel",
+                        "time": "2026-02-20 至 2026-02-23",
+                        "location": "上海市",
+                        "reason": "",
+                        "days": "4天",
+                        "transportMode": "火车",
+                    }
+                },
+            },
+        )
+
+        assert "| 申请类型 | 差旅费用申请 |" in response.answer
+        assert "| 申请类型 | travel |" not in response.answer
+
+
 def test_user_agent_application_edit_resubmits_returned_application_claim() -> None:
     session_factory = build_session_factory()
     with session_factory() as db: