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/utils/githubModelsCredentials.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, test } from 'bun:test'
+
+import {
+  clearGithubModelsToken,
+  readGithubModelsToken,
+  saveGithubModelsToken,
+} from './githubModelsCredentials.js'
+
+describe('readGithubModelsToken', () => {
+  test('returns undefined in bare mode', () => {
+    const prev = process.env.CLAUDE_CODE_SIMPLE
+    process.env.CLAUDE_CODE_SIMPLE = '1'
+    expect(readGithubModelsToken()).toBeUndefined()
+    if (prev === undefined) {
+      delete process.env.CLAUDE_CODE_SIMPLE
+    } else {
+      process.env.CLAUDE_CODE_SIMPLE = prev
+    }
+  })
+})
+
+describe('saveGithubModelsToken / clearGithubModelsToken', () => {
+  test('save returns failure in bare mode', () => {
+    const prev = process.env.CLAUDE_CODE_SIMPLE
+    process.env.CLAUDE_CODE_SIMPLE = '1'
+    const r = saveGithubModelsToken('abc')
+    expect(r.success).toBe(false)
+    expect(r.warning).toContain('Bare mode')
+    if (prev === undefined) {
+      delete process.env.CLAUDE_CODE_SIMPLE
+    } else {
+      process.env.CLAUDE_CODE_SIMPLE = prev
+    }
+  })
+
+  test('clear succeeds in bare mode', () => {
+    const prev = process.env.CLAUDE_CODE_SIMPLE
+    process.env.CLAUDE_CODE_SIMPLE = '1'
+    expect(clearGithubModelsToken().success).toBe(true)
+    if (prev === undefined) {
+      delete process.env.CLAUDE_CODE_SIMPLE
+    } else {
+      process.env.CLAUDE_CODE_SIMPLE = prev
+    }
+  })
+})
+