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/pages/index.ts

@@ -18,7 +18,6 @@ export { SkillsManagerPage } from './SkillsManagerPage';
 export { CommandsManagerPage } from './CommandsManagerPage';
 export { MemoryPage } from './MemoryPage';
 export { SettingsPage } from './SettingsPage';
-export { HelpPage } from './HelpPage';
 export { HookManagerPage } from './HookManagerPage';
 export { NotFoundPage } from './NotFoundPage';
 export { LiteTasksPage } from './LiteTasksPage';