Accessible toggle switch (ARIA switch role) for mounted admin pages.
Uses role="switch" and aria-checked per the ARIA Authoring
Practices Guide (APG). Keyboard users can activate via Space or
Enter. An optional hidden <input type="hidden"> can emit the
boolean form value when wired (see hidden_name attr).
The <button role="switch"> approach is preferred over a native
checkbox because it provides cleaner visual separation between
the toggle track/thumb and the label affordance.