Changes
PR #2224 by ksylvan: chore: remove GitHub Models provider integration and documentation
- Removed the GitHub Models provider from the compatible provider registry, dropping the integration entirely.
- Dropped GitHub API version headers from model discovery requests.
- Replaced GitHub cache fixtures with generic test providers and removed GitHub header verification along with its supporting test utilities.
- Deleted the GitHub Models setup documentation and the Copilot cross-reference.
- Removed GitHub Models listings from both the English and Chinese READMEs.