feat: add GitHub issue picker and API endpoints

Add GitHubIssuePickerDialog UI for selecting issues
Enable new session from GitHub issue from session sidebar
Implement GitHub issues/list/get/comments APIs across desktop, web, and VS Code

packages/ui/src/components/sections/openchamber/GitHubSettings.tsx

@@ -44,8 +44,10 @@ export const GitHubSettings: React.FC = () => {
     const desktop = (window as typeof window & { opencodeDesktop?: { openExternal?: (url: string) => Promise<unknown> } }).opencodeDesktop;
     if (desktop?.openExternal) {
       try {
-        await desktop.openExternal(url);
-        return;
+        const result = await desktop.openExternal(url);
+        if (result && typeof result === 'object' && 'success' in result && (result as { success?: boolean }).success === true) {
+          return;
+        }
       } catch {
         // fall through
       }