The executable integer-polynomial irreducibility checker is sound after
transport to Mathlib's polynomial model, under the standard certificate
side-conditions: each per-prime block uses a prime modulus, the input is
primitive, and the input is non-constant. Primality is needed for Rabin
irreducibility lifting and (ZMod p)[X] UFD reasoning; primitivity and
non-constancy rule out trivially reducible inputs whose recorded obstructions
would otherwise be vacuous.
Soundness of the kernel-reducible integer checker: a certificate accepted by
checkIrreducibleCertLinear on literal data certifies irreducibility of the
transported polynomial. The primality hypothesis feeds both the
Linear→committed checker implication and the committed checker's own
soundness theorem.
checkIrreducibleCertLinear_sound with every side condition stated as a
kernel-decidable Boolean check: primality of the recorded primes, content one,
and positive executable degree. This is the exact consumption shape of the
multi-prime arm of the factor_poly/irreducibility extension: it applies
this theorem (through zpolyIrreducible_of_checkIrreducibleCertLinear and
checkMultiPrimeCert) to a reified literal certificate with an
Eq.refl true proof in each hypothesis slot, so the whole obligation is
discharged by kernel reduction on literal data.