fix(scene): preserve prefab root on delete

[bofeng-song]

Problem

Deleting a select-all hierarchy in prefab editing mode could include the prefab root. CLI removed that root together with the selected nodes, and the editor later displayed anonymous Empty Node entries instead of retaining the prefab root and its name.

Creator keeps the opened prefab asset root in this case.

Cause

NodeService.delete() did not distinguish the current prefab editor root from regular nodes. A delete request targeting the root therefore removed the complete prefab hierarchy.

Fix

• Reject deletion when the current editor is in prefab mode and the target node UUID matches the opened prefab root UUID.
• Continue allowing child nodes to be deleted normally.
• Add a regression test that deletes a child and then attempts to delete the prefab root, verifying that the root path and name remain unchanged.

Validation

• npx tsc --noEmit --pretty false passes.
• The prefab integration suite could not start locally because the installed gl native module was built for a different Node ABI.