fix(builder): deep-clone node data on id regeneration to avoid shared props

regenerateTreeIds shallow-copied each node's data, leaving data.props (and
data.custom) as the same object reference between the original node and its
duplicate/pasted copy. Craft.js's setProp mutates data.props in place, so
editing the duplicate's props silently mutated the original too. Deep-clone
data via structuredClone before applying id remaps so no mutable sub-object
is shared between original and regenerated nodes.

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

craft/src/utils/craft-tree.ts

@@ -43,11 +43,18 @@ export function regenerateTreeIds(tree: NodeTree): NodeTree {
       newLinkedNodes[slot] = remapId(linkedId);
     }
 
+    // Deep-clone data so mutable sub-objects (props, custom, etc.) are never
+    // shared by reference between the original node and its regenerated
+    // copy. Craft.js's setProp mutates data.props in place, so a shallow
+    // copy here would let edits to the duplicate silently corrupt the
+    // original.
+    const clonedData = structuredClone(oldNode.data);
+
     const newNode: Node = {
       ...oldNode,
       id: newId,
       data: {
-        ...oldNode.data,
+        ...clonedData,
         parent: newParent,
         nodes: (oldNode.data.nodes || []).map(remapId),
         linkedNodes: newLinkedNodes,