fix(builder): regenerate node ids on duplicate/paste to prevent state corruption

Craft.js duplicate (ContextMenu + keyboard shortcut) and paste were reusing
the original node's toNodeTree() output verbatim, so addNodeTree() inserted
duplicate node ids into the editor tree. Added regenerateTreeIds() which
deep-clones a NodeTree and remaps rootNodeId, node map keys, node.id,
internal node.data.parent, node.data.nodes, and node.data.linkedNodes via
Craft.js's own getRandomId(). Also fixed pasteNode to insert as a sibling
of the right-clicked node (using its parent) instead of using a leaf node
as the new parent, which previously threw.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/panels/context-menu/ContextMenu.tsx

@@ -3,6 +3,7 @@ import { useEditor } from '@craftjs/core';
 import { findDeletableTarget } from '../../utils/craft-helpers';
 import { useSitesmithModal } from '../../state/SitesmithContext';
 import { buildSitesmithTarget } from '../../utils/sitesmith-target';
+import { regenerateTreeIds } from '../../utils/craft-tree';
 
 interface ContextMenuProps {
   visible: boolean;
@@ -65,15 +66,11 @@ export const ContextMenu: React.FC<ContextMenuProps> = ({
   const duplicate = useCallback(() => {
     if (!nodeId || nodeId === 'ROOT') return;
     try {
-      const tree = query.node(nodeId).toSerializedNode();
       const parentId = getParentId();
       if (!parentId) return;
 
-      // Get the full subtree
-      const freshTree = query.node(nodeId).toNodeTree();
-      const clonedTree = query.parseSerializedNode(freshTree.nodes[freshTree.rootNodeId].data).toNode();
-
-      actions.addNodeTree(freshTree, parentId);
+      const tree = regenerateTreeIds(query.node(nodeId).toNodeTree());
+      actions.addNodeTree(tree, parentId);
     } catch (e) {
       console.error('Duplicate failed:', e);
     }
@@ -92,10 +89,25 @@ export const ContextMenu: React.FC<ContextMenuProps> = ({
 
   const pasteNode = useCallback(() => {
     const sourceId = clipboardRef.current;
-    if (!sourceId) return;
+    if (!sourceId) {
+      onClose();
+      return;
+    }
     try {
-      const targetParent = nodeId || 'ROOT';
-      const tree = query.node(sourceId).toNodeTree();
+      if (!query.node(sourceId).get()) {
+        onClose();
+        return;
+      }
+
+      // Paste as a SIBLING of the right-clicked node, not as its child --
+      // using the clicked node itself as the parent throws when it's a leaf.
+      let targetParent = 'ROOT';
+      if (nodeId && nodeId !== 'ROOT') {
+        const clickedNode = query.node(nodeId).get();
+        targetParent = clickedNode?.data?.parent || 'ROOT';
+      }
+
+      const tree = regenerateTreeIds(query.node(sourceId).toNodeTree());
       actions.addNodeTree(tree, targetParent);
     } catch (e) {
       console.error('Paste failed:', e);