Codex instance
f37e08768d
Constrain the unique unit square to a closed D4 fundamental region once its placement is known. This preserves one representative of every board-orientation orbit without assigning identities to repeated squares. Keep a symmetry-disabled benchmark path, document the proof and measurements, and cover generic, diagonal, midline, corner, and centre orbits. Tests: Release, Debug, ASan, and UBSan CTest (11 passed each) Refs: #3