[Go]prompt.excute did not handle the additional message

**Describe the bug**
When I use prompt.excute, if I append a message, it won't be rendered and sent to the large model when it is actually sent。


**Screenshots**
<img width="1047" height="502" alt="Image" src="https://github.com/user-attachments/assets/519d2a83-e858-4e38-a9b2-0310f618733a" />

