nx_mesh_print_check_test.nx

nx_mesh_print_check_test.nx -- exercise bbox + manifold check on a synthetic tetrahedron and a deliberately broken mesh. Closed-form invariants: (a) Tetrahedron factory returns non-null mesh with 4 verts + 4 tris. (b) Bbox of unit tetrahedron = (0,0,0) to (EDGE,EDGE,EDGE). (c) Manifold check returns OK on the tetrahedron. (d) Manifold check returns NOT_MANIFOLD when one triangle is deleted (now 3 tris, three edges have no reverse partner). (e) Existing nx_mesh_validate still accepts the tetrahedron (no out-of-range indices). expect_exit: 0 license_tier: ORIGINAL