- Add SCSS for checkbox, radio, and switch controls with checked,
  disabled, and focus-visible states.
- Add Vue adapters GnCheckbox, GnRadio, GnRadioGroup, GnSwitch matching
  gnexus-ui-kit API.
- Wire components into plugin and entry exports.
- Add Choice controls demo partial and include it in demo/index.html.
- Extend Vue example app with interactive checkbox/radio/switch usage.
- Update component coverage matrix.