fix(card-sorting): end drag immediately when card becomes locked

Previously, if a card was dragged into its correct position (making
it part of the prefix/suffix), the drag would continue while the
auto-arrange effect tried to reposition it, causing thrashing.

Now:
- Check if card becomes locked during pointer move
- If locked, immediately release pointer capture and end drag
- Auto-arrange effect smoothly positions the card
- No more state thrashing

The card will smoothly animate to its correct position in the
prefix/suffix grid once it's determined to be correctly placed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/arcade-games/card-sorting/components/PlayingPhaseDrag.tsx

@@ -1464,6 +1464,15 @@ export function PlayingPhaseDrag() {
   const handlePointerMove = (e: React.PointerEvent, cardId: string) => {
     if (!dragStateRef.current || dragStateRef.current.cardId !== cardId) return
 
+    // Check if card has become locked during drag - if so, end the drag
+    if (isCardLocked(cardId)) {
+      const target = e.currentTarget as HTMLElement
+      target.releasePointerCapture(e.pointerId)
+      dragStateRef.current = null
+      setDraggingCardId(null)
+      return
+    }
+
     const { offsetX, offsetY } = dragStateRef.current
 
     // Calculate new position in pixels