- Derive MorphologyZone Default (#[default] AlluvialPlain), drop manual impl — clears the clippy --all-targets warning (pre-push gate). - Fix floor_at_voxel_z doc (described the inverse function). - Document floor_at_voxel_z / voxel_range_for_floor voxel-z as building-relative (base_floor = z:0) for #982-985 callers. - TODO(#957): districts keyed by city_id is a stub; use district_id. clippy --all-targets clean; 1259 lib tests pass. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>