修复报错

backend/app/engines/text_engine.py

@@ -416,6 +416,7 @@ class TextEngine(BaseEngine):
                                     },
                                 )
 
+            os.makedirs(output_dir, exist_ok=True)
             self._model.save_pretrained(output_dir)
             self._tokenizer.save_pretrained(output_dir)
             logger.info(f"PPO training completed for job {job_id}")