feat(web): remove /compact button from mobile keyboard accessory bar

Drops /compact from both the simple and extended accessory-bar layouts,
the action handler (case folded back to clear-only), the refocus guard,
and the JSDoc. /clear retains its double-tap confirmation. Verified on a
touch-emulated viewport: neither layout renders a compact action.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>