Wall expressIds that contributed an axis segment.
Length-unit scale that was applied to the extracted segments
(e.g. 0.001 for a millimetre model). Reported so callers can
scale their snap tolerance / min area to match.
Walls dropped by the extractor, with the reason.
Per-segment wall thickness in metres (parallel to segments /
contributingWallIds), from the wall's material layer set; undefined
when the wall carries no resolvable layer thickness. Used to inset the
centreline footprint to a net (inner-face) area.
Best-effort total wall count visible on the storey (existing + overlay).