v0.13.0 — certified ZEFOZ brackets for 167Er3+:Y2SiO5

Certified existence, curvature and stationary-point type of all twenty published nonzero-field ZEFOZ points of 167Er3+:Y2SiO5, both crystallographic sites. Transition brackets of width 4e-10 MHz, certified gradient bound 3.2e-37 MHz/mT, two-sided brackets on all three Hessian eigenvalues with certified signature, and Krawczyk existence plus local uniqueness within 2.9e-14 mT. At zero field an exact symbolic time-reversal identity certifies all 120 transitions stationary. The completeness question is reported dead per pre-registered kill condition. Three errata in the reference documented and versioned.