Forbid moving root instance

Author: TrySound

apps/builder/app/builder/features/navigator/navigator-tree.tsx

@@ -437,6 +437,10 @@ const getBuilderDropTarget = (
 };
 
 const canDrag = (instance: Instance, instanceSelector: InstanceSelector) => {
+  // forbid moving root instance
+  if (instanceSelector.length === 1) {
+    return false;
+  }
   if ($isContentMode.get()) {
     const parentId = instanceSelector[1];
     const parentInstance = $instances.get().get(parentId);