feat(config): default to WebSocket and migrate saved HTTP settings

tests/unit/test_llm_response_integrity.py

@@ -123,7 +123,7 @@ async def transport_case(monkeypatch, tmp_path, request):
     )
     llm_service._ENDPOINT_BREAKER._states.clear()
     llm_service._NON_STREAMING_ENDPOINTS.clear()
-    endpoint = ModelEndpoint(model_name="test-model", max_retries=0)
+    endpoint = ModelEndpoint(model_name="test-model", transport="http", max_retries=0)
     model = ModelFactory.create_model(endpoint)
     assert isinstance(model, ChatOpenAI)
     yield SimpleNamespace(