[错误] OpenAI 响应流: tool-call-args-delta/tool-call-ready 永远不发送 (callBuffers 以 call_id 为键,但事件携带 item_id) — MCPAgent.stream() 返回为零步骤

Describe the bug

On the OpenAI Responses streaming path, streamResponsesTurn keys its tool-call buffers (callBuffers) by call_id, but the streaming events that carry the arguments — response.function_call_arguments.delta and response.function_call_arguments.done — do not have a call_id field; they carry item_id (the output-item id, fc_...) and output_index only. So the buffer lookup key is always the fallback "" and callBuffers.get("") is always undefined. Neither tool-call-args-delta nor tool-call-ready is ever emitted.