Collision stays hand-rolled because it is the reference for a future GPU
kernel, but its inputs now come from Clipper region offsets. Pin down that
lines-only, round-join, 1e-4-precision polygons keep the contact and
part-in-part semantics: a neighbor inside a collapsed slot, a part inside
a hole that shrank by the spacing, and zero-spacing edge contact.
Document which steps are per-polygon preparation to cache and upload once,
and which are per-pair kernel-shaped work.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ajandClaude Opus 5.5
dceb5f7d18