Variant skill: what it does and how to install it

What it does. Takes one UI component, reads its surrounding styles, tokens and layout, then builds three purposefully different variants around one axis such as structure, density, emphasis, type or voice. It hosts them on the real page behind a grouped picker, selectable with a ?__variant= URL, and checks each against accessibility and responsive requirements.

When to use it. Use it to explore alternatives before choosing a direction, then promote the selected variant and remove the harness. It is not for reviewing existing UI, stress-testing one component or mapping its states; those belong to separate skills.