Modelled threads (Thread with modeled: true): the ISO 68-1 profile cut along a helix, M3 to M20, on shafts and in bores; running out past a free end of the face, stopping square at a set length. The groove is a watertight screw-sweep mesh (kernel::sweep_helix_mesh) cut by kernel::faceted_boolean (BSP on the faceted body, tolerance ladder checked by A−B + A∩B = A); the polygon rebuild welds vertices across grid cells, splits pinched loops, finds T-junctions through a grid, and takes the group's plane for a loop a hair off flat

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/engine/src/lib.rs

@@ -429,3 +429,5 @@ impl Session {
 mod extent_tests;
 #[cfg(test)]
 mod tests;
+#[cfg(test)]
+mod thread_tests;