fix(dnd): validate proposed hover destinations

packages/block-editor/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@wrnexus/block-editor",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "type": "module",
   "description": "Hydrated accessible editor runtime for WRNexus block documents.",
   "exports": {

packages/block-editor/src/runtime.ts

@@ -7,6 +7,10 @@ export interface MountedEditor {
 export interface MountEditorOptions {
   direction?: "ltr" | "rtl";
   announce?(announcement: DndAnnouncement): string;
+  canMove?(intent: {
+    nodeIds: string[];
+    to: { parentId: string; slot: string; index: number };
+  }): boolean;
   onMove(intent: {
     nodeIds: string[];
     to: { parentId: string; slot: string; index: number };
@@ -37,6 +41,19 @@ export function mountBlockEditor(root: HTMLElement, options: MountEditorOptions)
     let gesture = 0;
     const groups = new Map<string, { parentId: string; slot: string }>();
     manager = createDndManager({
+      accept(ids, location) {
+        const destination = groups.get(String(location.group));
+        return (
+          !destroyed &&
+          generation === currentGeneration &&
+          !!destination &&
+          (options.canMove?.({
+            nodeIds: ids.map(String),
+            to: { ...destination, index: location.index },
+          }) ??
+            true)
+        );
+      },
       direction:
         options.direction ?? (view.getComputedStyle(root).direction === "rtl" ? "rtl" : "ltr"),
       reducedMotion: view.matchMedia("(prefers-reduced-motion: reduce)").matches,