using message_file event instead of message event (#22988)

api/core/app/task_pipeline/message_cycle_manager.py

     MessageFileStreamResponse,
     MessageReplaceStreamResponse,
     MessageStreamResponse,
+    StreamEvent,
     WorkflowTaskState,
 )
 from core.llm_generator.llm_generator import LLMGenerator
         :param message_id: message id
         :return:
         """
+        message_file = db.session.query(MessageFile).filter(MessageFile.id == message_id).first()
+        event_type = StreamEvent.MESSAGE_FILE if message_file else StreamEvent.MESSAGE
+
         return MessageStreamResponse(
             task_id=self._application_generate_entity.task_id,
             id=message_id,
             answer=answer,
             from_variable_selector=from_variable_selector,
+            event=event_type,
         )
 
     def message_replace_to_stream_response(self, answer: str, reason: str = "") -> MessageReplaceStreamResponse: