Irrationality of cubic threefolds after one stabilization

The primary manuscript proves that X times P1 is irrational for every smooth complex cubic threefold X. Its proof decomposes the generic even quantum D-module into blocks, records their isomorphism classes in a free commutative monoid, and applies an additive rank-two formal-exponent marker. The marker vanishes on all point, curve, and surface centers, doubles under product with P1, detects the cubic block, and vanishes on projective space. The paper also gives a quantum-D-module irrationality criterion for smooth projective threefolds and the one-stabilization theorem for prime Fano threefolds of genus eight. This repository release includes two separate companion manuscripts: one constructs primitive minimal classes and universal CH0-triviality on the nonstandard A5-invariant cubic pencil; the other studies a finer framed formal-monodromy count, whose cubic and product calculations are unconditional while its operation formulas and birational invariance retain explicitly stated hypotheses. A shared Mathlib reviewer artifact records the formal coverage and trust boundary of all three manuscripts. The count and its exact residue-discriminant refinement extend additively to K0(Var_C)/(L-1), distinguish examples with equal Hodge diamonds, and constrain the centers in rationalizing weak factorizations. These extensions are proved in the manuscript and are not formalized in Lean.