Caveats

(i) Both independent reviews ran on the same box as the author (shared Python/sympy and TeX Live). (ii) The D01/D03 pole values were never recomputed from independent Feynman rules; they are cross-checked only through the exact cancellation of the $c\cdot h$ defect in $d$. (iii) Full ${\sigma }_0$ closure and the $c\cdot h$ defect rely on the earlier p19–p22 independent checks. (iv) D06 is accepted through its exact equality with XVI-P P15 $\Sigma$.