A release that ended a started drag fired the frame's `OnMouseUp` before `OnDragStop`, so a frame that both drags and acts on mouse-up ran its mouse-up action at the end of every drag.
In the reference, the mouse-up first checks the frame's drag registration for the released button and its started drag: if both hold it fires `OnDragStop` and the hover frame's `OnReceiveDrag`, and returns before `OnMouseUp`, which only a release without a started drag reaches.
The release now follows that: a started drag fires `OnDragStop` and the drop in `OnMouseUp`'s place, and any other release fires `OnMouseUp` as before.
Tests cover a drag, a plain click, a button the frame is not registered to drag, and a resize grip.
Fixes#920
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>