[Bug] 当发送图片时产生错误的 token 占用计数

发送图片时

<img width="2334" height="398" alt="Image" src="https://github.com/user-attachments/assets/624d8694-db38-4ecf-a8a7-b3c9babb50fd" />

正常情况

<img width="2476" height="270" alt="Image" src="https://github.com/user-attachments/assets/5a6a2227-4c7e-4977-9c25-92835c98042a" />