fix(ui): polish board→rack recall drag and its gesture interplay

- The rack now animates the opening drop gap for a board-tile recall drag too
  (the reorder transition was gated on a rack-source drag only).
- While a board tile is dragged over the rack (a recall, gap shown), the ✅
  confirm and its preview caption are hidden so they don't sit over the gap;
  they return if the tile is dragged back out over the board.
- A recall drop lands off the boardwrap, so its pointerup never reached the
  boardwrap handler and left a stale id in the active-pointer set — the next
  board swipe then read as multi-touch and the shuffle / history pull went dead.
  Reconcile the pointer when a drag ends or cancels. Regression e2e added.

ui/src/game/Rack.svelte

@@ -56,7 +56,7 @@
   }
 </script>
 
-<div class="rack" class:reordering={draggingId != null} class:landscape data-rack>
+<div class="rack" class:reordering={draggingId != null || dropIndex != null} class:landscape data-rack>
   {#each shown as slot, i (slot.id)}
     <button
       class="tile"