feat(blocks): add reusable application shell blocks
- add appearance state, theme presets, preference controls, and preview components
- add responsive primary, nested, mobile, and flyout navigation with route-aware breadcrumbs
- add application layout, sidebar state, header actions, user menu, query refresh, and scroll utilities
- add configurable chat and notification surfaces backed by consumer-provided data and queries
- expose package entry points and cover theme, state, and command behavior with tests
Maofeng
011e7d8115