sync model validation with cli catalog

tradingagents/llm_clients/openai_client.py

@@ -41,6 +41,7 @@ class OpenAIClient(BaseLLMClient):
 
     def get_llm(self) -> Any:
         """Return configured ChatOpenAI instance."""
+        self.warn_if_unknown_model()
         llm_kwargs = {"model": self.model}
 
         if self.provider == "xai":