fix(dnd): validate proposed hover destinations

packages/dnd/src/manager.ts

@@ -36,7 +36,10 @@ export function createDndManager(options: DndManagerOptions): DndManager {
     const source = event.operation.source as
       (typeof event.operation.source & { group?: string | number; index?: number }) | null;
     if (!source) return;
-    const destination = { group: source.group ?? "default", index: source.index ?? 0 };
+    const target = event.operation.target as
+      (typeof event.operation.target & { group?: string | number; index?: number }) | null;
+    if (!target) return;
+    const destination = { group: target.group ?? "default", index: target.index ?? 0 };
     if (options.accept && !options.accept(activeIds, destination)) {
       event.preventDefault();
       options.announce?.({ type: "invalid", ids: activeIds, location: destination });