test: align backend boundary and schema contract tests with current behavior

test/api/test_chat_backend_boundary.py

@@ -48,6 +48,7 @@ async def test_non_stream_chat_uses_backend_neutral_result():
             session_id="session-001",
             text="发生了交通事故",
             need_form_update=True,
+            client_mode="direct",
         )
     ]
 

test/api/test_public_schema_contract.py

@@ -83,6 +83,7 @@ def test_chat_request_defaults_are_backward_compatible() -> None:
 
     assert request.model_dump() == {
         **chat_request_payload(),
+        "clientMode": "direct",
         "needFormUpdate": False,
         "useTextChunk": False,
     }
@@ -159,7 +160,7 @@ def test_required_fields_remain_required(
         (ProcessRequest_get, get_request_payload, "sessionId", "s" * 65),
         (ProcessRequest_set, set_request_payload, "timeStamp", "t" * 33),
         (ProcessResponse_chat, chat_response_payload, "nextStage", "n" * 33),
-        (ProcessResponse_chat, chat_response_payload, "nextStageCode", "10020"),
+        (ProcessResponse_chat, chat_response_payload, "nextStageCode", "s" * 33),
         (ProcessResponse_chat, chat_response_payload, "code", "10000"),
         (ProcessResponse_get, get_response_payload, "code", "10000"),
         (ProcessResponse_set, set_response_payload, "code", "10000"),