avoid Python code module conflict in s01

[weyWong-code]

Summary

Update the S01 agent loop to terminate explicitly when the model returns
stop_reason == "end_turn".

Motivation

之前的条件会将除 tool_use 之外的所有响应都视为当前轮次已经完成，显式判断 end_turn 可以更清楚地表达
The previous condition treated every response other than tool_use as a
completed turn:

if response.stop_reason != "tool_use":
    return