Function closest_points_on_triangles

pub fn closest_points_on_triangles(
    first: [DVec3; 3],
    second: [DVec3; 3],
) -> Result<ClosestPoints3, ProximityError>

Deterministic metric witnesses on two non-degenerate triangles.

Candidate ties retain this stable order: first-triangle vertices, second-triangle vertices, then first/second edge pairs lexicographically. This function does not certify intersection; pair it with scalar predicates when zero separation changes control flow.