- Guard _buildCache in merged-outline-node against stale/disposed
Object3D refs that cause TypeError on .id access during render
- Reset children array when duplicating roofs to prevent inconsistent
parent-child relationships (matching existing stair behavior)
- Use obj?.parent check in EditorOutlinerSync to ensure objects are
still in the scene graph before adding to outliner arrays
- Resume temporal state on parse failure to prevent undo/redo freeze
Closes#232
