Rewrites three commented-out tests to access public fields directly instead of the removed item_by_name/item_index/is_group_collapsed methods: - add_item_in_group_sets_group: uses items.get() - item_index_reflects_insertion_order: uses items.get_index_of() - toggle_group_collapse_toggles_twice + involutive proptest: inspect collapsed_groups directly Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>