feat(ui): Add pointer coordinates and drop zone rect to ct-drop event (commontoolsinc#2223)

The ct-drop-zone component now emits additional data in the ct-drop event:
- pointerX/pointerY: The cursor coordinates at drop time
- dropZoneRect: The bounding rect of the drop zone (left, top, width, height)

This enables patterns to calculate precise drop positions within the zone,
which is necessary for implementing drag-and-drop features like placing
tiles on a game board where shadow DOM isolation prevents DOM queries.

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

Co-authored-by: tonyespinoza1 <tonyespinoza1@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: tonyespinoza1

packages/ui/src/v2/components/ct-drop-zone/ct-drop-zone.ts

@@ -164,10 +164,21 @@ export class CTDropZone extends BaseElement {
       // Emit leave event before drop (dropping is a form of leaving)
       this.emit("ct-drag-leave", {});
 
-      // Emit drop event
+      // Get drop zone bounding rect for position calculation in handler
+      const dropZoneRect = this.getBoundingClientRect();
+
+      // Emit drop event with pointer coordinates and drop zone rect
       this.emit("ct-drop", {
         sourceCell: dragState.cell,
         type: dragState.type,
+        pointerX: dragState.pointerX,
+        pointerY: dragState.pointerY,
+        dropZoneRect: {
+          left: dropZoneRect.left,
+          top: dropZoneRect.top,
+          width: dropZoneRect.width,
+          height: dropZoneRect.height,
+        },
       });
     }
   }