test(components): add component test infrastructure
- test-page.html: Test page with all components configured
- components.spec.ts: Playwright tests for all components
- Button: variants, sizes, disabled, loading, click events
- Card: slots, interactive, selected
- List: items, keyboard nav, disabled
- Input: text input, disabled, suggestions
- Select: native and custom modes
- Switch: checked state, toggle, disabled
- Dialog: open/close
- Tabs: selection, panel visibility
- Details: open/close toggle
- Dropdown: trigger, open/close
- Button Group: selection
- Accessibility: ARIA roles and attributes