- helpers/placement: port get_storey_elevation (placement Z, falling back
to the Elevation attribute), matching ifcopenshell.util.placement.
- Add a secondary column: the storey elevation for IfcBuildingStorey,
otherwise the LongName when filled. Elevations are right-aligned.
- Columns: Name is drag-resizable (interactive) and defaults to 20% of the
width, Long Name stretches to fill the rest, and the eye is pinned to the
right at a fixed width. Header shown so the divider can be grabbed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>