Finish reordering from the stored egui drag owner and primary-button
release even when wheel scrolling culls the originating row. Cancel
disabled, interrupted or stale gestures before they can arrange layers.
Cover scrolling in both directions, selected groups, Undo/Redo, later
drags and cancellation boundaries, including opening Settings mid-drag.
Make the existing no-op control cross the drag threshold.
Fixes#2492.
WillPastor
4fccf2a3b7