Changes
PR #1839 by ksylvan: Add GitHub Models Provider and Refactor Fetching Fallback Logic
- Add GitHub Models provider and refactor model fetching with direct API fallback
- Add GitHub Models to supported OpenAI-compatible providers list
- Implement direct HTTP fallback for non-standard model responses
- Centralize model fetching logic in openai package
- Upgrade openai-go SDK dependency from v1.8.2 to v1.12.0