AABB min corner over start+end positions [x, y, z].
AABB max corner over start+end positions [x, y, z].
Max finite half-width over start/end widths — the conservative
per-segment footprint used to expand the cull box (matches
computeLineBounds' expansion semantics exactly).
Processed lines data ready for GPU rendering.
After nD clipping and 3D projection: