rank 4: n=3, forms (rhombi + coordinates)=21, candidates z=8 (max coordinate 1), level-2 boxes: 64
boxes tested per level: [(2, 64)]; boxes of the partition per level: [(2, 64)]; total 64; volume 1; unresolved: []; distinct z used: 8; 0.1s
RESULT rank 4: [0,1)^3 is partitioned into 64 half-open dyadic boxes, each contained in an integer translate of U+ (certificate cover_r4.json). Hence (ii+) and (ii) hold for rank 4; no vertex lemma used.
