The button variant names in the explorer (primary, secondary, etc.) don't match the UI kit design system. For example, secondary renders as the branded/blue style when it should be grey, and there is no primary variant defined at all.

The variant list in Button.svelte needs to be reconciled with the UI kit so the naming is consistent.

cc @brandonhaslegs (z6MkpwnLQxFBQXyMK3Es91s8A7Ew7G11BFFyng1dqZR8QhG3)