Dragging the brightness slider on the wall panel set the handle and
published nothing; tapping a point on the track worked. The control is a
native range input laid transparent over the drawn track, and only the
release publishes — but the input never said the drag was its own. On a
touch panel a sideways swipe is a pan, or a back-navigation, so the
browser took the pointer over mid-drag and ended it in `pointercancel`.
The value had followed the finger and was never sent.
`touch-action: none`, as the colour disk beside it has always had. The
release also answers `pointercancel` and `lostpointercapture` now, which
covers a mouse let go outside the input and leaves no way for a draft to
sit there unpublished.
Two checks: a drag across the track reaches the engine, and the input
still owns its gesture. The second fails against a build without the
CSS, which is what makes it worth having.
