ComputeNormal assumed CW winding for all contours. For CCW-wound cutouts,
line normals pointed to the material side instead of scrap, placing lead-ins
on the wrong side. Now accepts a winding parameter: lines flip the normal
for CCW winding, and arcs flip when arc direction differs from contour
winding (concave feature detection).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
AJ Isaacs
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