Introduce new events: $onDragCommitted and $onDragTransformed

[jalal246]

This PR adds two new drag end events: $onDragCommitted and $onDragTransformed. These allow consumers to handle drag endings differently depending on whether the drag was committed to the DOM or just transformed.

Both event payloads emit the following details:

type PayloadDragMutation = {
  /** Represents the main category of the drag event. */
  type: typeof DRAG_CAT;

  /** Indicates the timestamp when the event occurred. */
  timestamp: number;

  /** Targeted elements */
  element: HTMLElement;

  indexes: {
    /** The initial index of the moved element. */
    initial: number;

    /** The index where it was inserted in the receiving container. */
    inserted: number;
  };

  containers: {
    /** The container from which the element originated. */
    origin: HTMLElement;

    /** The container where the element is now located. */
    target: HTMLElement;
  };
}

The $onDragCommitted event is fired when a drag ends and changes are reconciled back to the data store. The $onDragTransformed event is fired if there is no reconciliation, but the element is transformed visually.

The motivation for this change is to allow consumers to handle committed drags differently than drags that were just transformed with no data changes. For example, triggering a re-render or data fetch on commit but not on transform.

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
packages/dflex-dnd/dist/dflex-dnd.mjs	11.78 KB (+0.29% 🔺)	236 ms (+0.29% 🔺)	328 ms (+29.54% 🔺)	564 ms
packages/dflex-core-instance/dist/dflex-core.mjs	60 B (0%)	10 ms (0%)	357 ms (+121.06% 🔺)	367 ms
packages/dflex-dom-gen/dist/dflex-dom.mjs	23 B (0%)	10 ms (0%)	245 ms (+1.05% 🔺)	255 ms
packages/dflex-store/dist/dflex-store.mjs	244 B (0%)	10 ms (0%)	171 ms (-43.22% 🔽)	181 ms
packages/dflex-utils/dist/dflex-utils.mjs	263 B (0%)	10 ms (0%)	189 ms (+16.42% 🔺)	199 ms
packages/dflex-draggable/dist/dflex-draggable.mjs	5.99 KB (+0.18% 🔺)	120 ms (+0.18% 🔺)	223 ms (-30.06% 🔽)	343 ms