未启用max_completion_tokens时默认传递max_tokens=1048576，导致报错

与https://github.com/AQBot-Desktop/AQBot/issues/93 类似的问题

<img width="569" height="210" alt="Image" src="https://github.com/user-attachments/assets/8a48d5ca-f6b4-4bda-8652-462404bc934c" />

<img width="601" height="40" alt="Image" src="https://github.com/user-attachments/assets/f066db22-f27e-48be-a9fe-fa8e218a7980" />