Add GitHub integration for PRs, issues and AI PR description (#205)

* feat: integrate GitHub OAuth device flow across runtimes

Add GitHub OAuth device flow endpoints across runtimes
Introduce GitHubSettings UI panel and sidebar entry
Persist GitHub auth state in per-runtime storage

* feat: add GitHub PR status and PR description generation

Show PR status for the current branch in the Git view
Generate a pull request description from the diff between base and head
Expose prStatus, prCreate, and prMerge APIs in web and desktop clients

* feat: add GitHub PR ready for review

Add API to mark pull requests as ready for review
Show a Ready button for draft PRs and reflect status in UI
Handle token expiration and GraphQL errors when marking ready

packages/vscode/webview/api/index.ts

@@ -6,6 +6,7 @@ import { createVSCodeToolsAPI } from './tools';
 import { createVSCodeEditorAPI } from './editor';
 import { createVSCodeGitAPI } from './git';
 import { createVSCodeActionsAPI } from './vscode';
+import { createVSCodeGitHubAPI } from './github';
 
 // Stub APIs return sensible defaults instead of throwing
 const createStubTerminalAPI = (): TerminalAPI => ({
@@ -29,6 +30,7 @@ export const createVSCodeAPIs = (): RuntimeAPIs => ({
   settings: createVSCodeSettingsAPI(),
   permissions: createVSCodePermissionsAPI(),
   notifications: createStubNotificationsAPI(),
+  github: createVSCodeGitHubAPI(),
   tools: createVSCodeToolsAPI(),
   editor: createVSCodeEditorAPI(),
   vscode: createVSCodeActionsAPI(),