<x-toggle> renders data-md-toggle, its row (data-md-right), track,
handle and icons as data-md-* attributes; the handle's icons take size
16 and a label-less track md-touch-target (plan step 36). toggle.css
gains the root; a browser test pins the handle's 16px/24px sizes and
16px/36px centres off and on.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9