fix(backend): handle reasoning event correctly

backend/src/agent.py

@@ -115,7 +115,21 @@ class Agent:
                 'threadId': message.thread_id,
             })
 
-        await run.on_async('output', on_output_event)
+        async def on_reasoning_event(stream):
+            print("[agent] run output " + repr(stream))
+            new_message = await self.app.send_chat_message(
+                sender=self.id,
+                chat_id=message.chat_id,
+                thread_id=message.thread_id,
+                content=stream,
+            )
+            run.emit_event('chat-message', {
+                'messageId': new_message['id'],
+                'chatId': message.chat_id,
+                'threadId': message.thread_id,
+            })
+
+        await run.on_async('reasoning', on_reasoning_event)
 
         await self.run(run)
         return run