refactor: decouple docs-site from ccw monorepo

- Remove docs-frontend.ts utility and docs proxy from server.ts
- Remove docs startup logic from serve.ts
- Delete HelpPage.tsx and /help route from frontend
- Remove help navigation entry from Sidebar.tsx
- Clean /docs proxy from vite.config.ts
- Remove docs-related scripts from package.json files
- Delete help.spec.ts E2E tests
- Remove docs-site directory (migrated to D:\ccw-doc)

The docs-site has been moved to D:\ccw-doc as a standalone Docusaurus
project with baseUrl='/' for static hosting deployment (GitHub Pages/Netlify).

ccw/frontend/src/components/layout/Sidebar.tsx

@@ -14,7 +14,6 @@ import {
   Terminal,
   Brain,
   Settings,
-  HelpCircle,
   PanelLeftClose,
   PanelLeftOpen,
   LayoutDashboard,
@@ -112,7 +111,6 @@ const navGroupDefinitions: NavGroupDef[] = [
       { path: '/settings/codexlens', labelKey: 'navigation.main.codexlens', icon: Sparkles },
       { path: '/api-settings', labelKey: 'navigation.main.apiSettings', icon: Server },
       { path: '/settings', labelKey: 'navigation.main.settings', icon: Settings, end: true },
-      { path: '/help', labelKey: 'navigation.main.help', icon: HelpCircle },
     ],
   },
 ];