zulip-0001: user_groups.py lock_subgroups_with_respect_to_supergroup group_ids_found list O(G*F) -> set O(G+F), 142x at N=1000
zulip-0002: user_groups.py update_user_group group_ids_found list O(D*F) -> set O(D+F), 76x at N=1000
zulip-0003: actions/user_groups.py update_users_in_full_members_system_group full_member_group_user_ids list O(M*F) -> set O(M+F), 55x at N=1000
Previous shallow scan marked CLEAN; deeper scan found all 3. MOAD-0002/0003/0004/0005 CLEAN.
3/3 unit tests PASS.