feat: add support for GitHub Models provider

- Introduced environment variable CLAUDE_CODE_USE_GITHUB to enable GitHub Models.
- Added checks for GITHUB_TOKEN or GH_TOKEN for authentication.
- Updated base URL handling to include GitHub Models default.
- Enhanced provider detection and error handling for GitHub Models.
- Updated relevant functions and components to accommodate the new provider.

src/components/StartupScreen.ts

@@ -80,6 +80,7 @@ const LOGO_CLAUDE = [
 
 function detectProvider(): { name: string; model: string; baseUrl: string; isLocal: boolean } {
   const useGemini = process.env.CLAUDE_CODE_USE_GEMINI === '1' || process.env.CLAUDE_CODE_USE_GEMINI === 'true'
+  const useGithub = process.env.CLAUDE_CODE_USE_GITHUB === '1' || process.env.CLAUDE_CODE_USE_GITHUB === 'true'
   const useOpenAI = process.env.CLAUDE_CODE_USE_OPENAI === '1' || process.env.CLAUDE_CODE_USE_OPENAI === 'true'
 
   if (useGemini) {
@@ -88,6 +89,13 @@ function detectProvider(): { name: string; model: string; baseUrl: string; isLoc
     return { name: 'Google Gemini', model, baseUrl, isLocal: false }
   }
 
+  if (useGithub) {
+    const model = process.env.OPENAI_MODEL || 'github:copilot'
+    const baseUrl =
+      process.env.OPENAI_BASE_URL || 'https://models.github.ai/inference'
+    return { name: 'GitHub Models', model, baseUrl, isLocal: false }
+  }
+
   if (useOpenAI) {
     const model = process.env.OPENAI_MODEL || 'gpt-4o'
     const baseUrl = process.env.OPENAI_BASE_URL || 'https://api.openai.com/v1'