- Implement `/api/clusters/[id]/folders` endpoint for folder navigation with pagination and error handling
- Create ClusterFolderView component for folder tab UI with breadcrumb and cluster theming
- Enhance VirtualizedFolderGrid to support cluster API mode and handle cluster folder responses
- Integrate folder view as default tab on cluster page with navigation and state management
- Add comprehensive testing documentation and handle loading, empty, and error states in UI
