Cut-off scrap lines were a solid 1.5px near-black stroke that read like
another sheet/part outline. They now render as a 2px orange-red dash so
operators can spot scrap cuts at a glance, and the manual cut-off preview
is recolored to match the applied line. Selected cut-offs keep their solid
blue highlight.
Add bitmap regression tests (CutOffDisplayTests) that verify the dashed
orange style, the dashed gaps, and the unchanged selection highlight.
