message: improve StructureSelectionManager.onUpdate
  only process for root structure (processing childs is superfluous)
diff: @@ -245,7 +245,6 @@ export class StructureSelectionManager extends StatefulPluginComponent<Structure
  }
  private onUpdate(ref: string, oldObj: PSO.Molecule.Structure | undefined, obj: PSO.Molecule.Structure) {
  -
  // no change to structure
  if (oldObj === obj || oldObj?.data === obj.data) return;
  @@ -253,7 +252,9 @@ export class StructureSelectionManager extends StatefulPluginComponent<Structure
  const cell = this.plugin.helpers.substructureParent.get(obj.data, true);
  if (!cell) return;
  - ref = cell.transform.ref;
  + // only need to update the root
  + if (ref !== cell.transform.ref) return;
  +
  if (!this.entries.has(ref)) return;
  // use structure from last decorator as reference
  