Can't login after change the github account credential.

- Copilot for Xcode: [e.g. 0.47.0]
- Xcode: 16.2
- macOS: 15.7

1. Install copilot and use. 
2. changed github login email address, and token.
3. copilot doesn't work

**Screenshots**

<img width="877" height="597" alt="Image" src="https://github.com/user-attachments/assets/8aaf8410-cf32-4d04-86f2-69b69fc42bb3" />
