[Primitive] Checkbox

[jbatte47]

Summary

Introduce a Checkbox primitive for binary selection.

Intended role in Lattice

Checkbox provides a token-driven, accessible binary control without domain logic.

Proposed API

• checked / onCheckedChange (controlled)
• indeterminate: true | false
• size: sm | md | lg
• state: default | invalid | disabled | loading

Variants

• size: sm | md | lg
• state: default | invalid | disabled | loading

Non-goals

• Does not implement group behavior (use composition).
• Does not accept arbitrary colors.

States

• default | hover | focus-visible | checked | indeterminate | invalid | disabled | loading.

Accessibility checklist

• Supports keyboard toggle behavior.
• Uses aria-checked for indeterminate state.
• Focus-visible styles required.