[错误]: 取消 RealtimeAgent.reply_stream 会留下一个消费未来事件的读取器

From a repository checkout, save the following as `reproduce_stream_cancel.py` and run `PYTHONPATH=src:tests Python reproduce_stream_cancel.py`. It reuses the existing offline test model/transport; no provider credentials, audio hardware, or network access are required. Private state is inspected only to synchronize the reproduction with the waiting reader and provider response.