fix: draw small radii on large bodies round (#515)

Display meshes also bound the angle one facet turns, so bends and small holes on a large body are drawn round instead of as chamfers or squares. Bounded per face, and only the display mesh changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/lib.rs

@@ -793,6 +793,8 @@ mod construct_tests;
 #[cfg(test)]
 mod delete_face_tests;
 #[cfg(test)]
+mod display_mesh_tests;
+#[cfg(test)]
 mod extent_tests;
 #[cfg(test)]
 mod hole_face_tests;