refactor(backend): update services and tests

- services/expense_claims.py: update expense claims service
- services/user_agent.py: update user agent service
- tests/test_orchestrator_service.py: update orchestrator service tests
- tests/test_user_agent_service.py: update user agent service tests

server/src/app/services/user_agent.py

@@ -207,6 +207,8 @@ class UserAgentService:
 
         if payload.ontology.intent == "draft":
             tool_message = str(payload.tool_payload.get("message") or "").strip()
+            if payload.tool_payload.get("draft_limit_reached"):
+                return tool_message or "你当前已保存 3 个草稿，请先完成已保存的草稿，才能再次新建草稿。"
             if tool_message and (
                 str(payload.tool_payload.get("claim_id") or "").strip()
                 or str(payload.tool_payload.get("claim_no") or "").strip()
@@ -988,6 +990,11 @@ class UserAgentService:
             return None
         if payload.ontology.intent not in {"draft", "operate"}:
             return None
+        if payload.tool_payload.get("draft_limit_reached"):
+            return (
+                str(payload.tool_payload.get("message") or "").strip()
+                or "你当前已保存 3 个草稿，请先完成已保存的草稿，才能再次新建草稿。"
+            )
 
         review_action = str(payload.context_json.get("review_action") or "").strip()
         if review_action == "save_draft":