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/commands.ts

@@ -19,6 +19,7 @@ import cost from './commands/cost/index.js'
 import diff from './commands/diff/index.js'
 import ctx_viz from './commands/ctx_viz/index.js'
 import doctor from './commands/doctor/index.js'
+import onboardGithub from './commands/onboard-github/index.js'
 import memory from './commands/memory/index.js'
 import help from './commands/help/index.js'
 import ide from './commands/ide/index.js'
@@ -288,6 +289,7 @@ const COMMANDS = memoize((): Command[] => [
   memory,
   mobile,
   model,
+  onboardGithub,
   outputStyle,
   remoteEnv,
   plugin,