safe cell cross-check of results/U_015_1_cert.jsonl.gz: 160 of 30724 zone-A cells at prec=96 on 8 workers
    [20/160] min safe margin so far +1.08e-05
    [40/160] min safe margin so far +1.08e-05
    [60/160] min safe margin so far +1.08e-05
    [80/160] min safe margin so far +1.08e-05
    [100/160] min safe margin so far +1.08e-05
    [120/160] min safe margin so far +1.08e-05
    [140/160] min safe margin so far +1.08e-05
    [160/160] min safe margin so far +1.08e-05
done: 160 cells, 0 safe failures, 0 cells with fast>safe; min safe-method margin = +1.08e-05  (coverage of [0.15,1.0] established by check_cert_U)
