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/services/api/providerConfig.github.test.ts

@@ -0,0 +1,41 @@
+import { afterEach, expect, test } from 'bun:test'
+
+import {
+  DEFAULT_GITHUB_MODELS_API_MODEL,
+  normalizeGithubModelsApiModel,
+  resolveProviderRequest,
+} from './providerConfig.js'
+
+const originalUseGithub = process.env.CLAUDE_CODE_USE_GITHUB
+
+afterEach(() => {
+  if (originalUseGithub === undefined) {
+    delete process.env.CLAUDE_CODE_USE_GITHUB
+  } else {
+    process.env.CLAUDE_CODE_USE_GITHUB = originalUseGithub
+  }
+})
+
+test.each([
+  ['copilot', DEFAULT_GITHUB_MODELS_API_MODEL],
+  ['github:copilot', DEFAULT_GITHUB_MODELS_API_MODEL],
+  ['', DEFAULT_GITHUB_MODELS_API_MODEL],
+  ['github:gpt-4o', 'gpt-4o'],
+  ['gpt-4o', 'gpt-4o'],
+  ['github:copilot?reasoning=high', DEFAULT_GITHUB_MODELS_API_MODEL],
+] as const)('normalizeGithubModelsApiModel(%s) -> %s', (input, expected) => {
+  expect(normalizeGithubModelsApiModel(input)).toBe(expected)
+})
+
+test('resolveProviderRequest applies GitHub normalization when CLAUDE_CODE_USE_GITHUB=1', () => {
+  process.env.CLAUDE_CODE_USE_GITHUB = '1'
+  const r = resolveProviderRequest({ model: 'github:gpt-4o' })
+  expect(r.resolvedModel).toBe('gpt-4o')
+  expect(r.transport).toBe('chat_completions')
+})
+
+test('resolveProviderRequest leaves model unchanged without GitHub flag', () => {
+  delete process.env.CLAUDE_CODE_USE_GITHUB
+  const r = resolveProviderRequest({ model: 'github:gpt-4o' })
+  expect(r.resolvedModel).toBe('github:gpt-4o')
+})