Irreducible Torsion Sectors and Two-Layer Contracted α-Surface Linearity

This paper classifies contracted torsionful α\alphaα-surface linearity by irreducible Riemann-Cartan torsion sector. It separates representation-allowed, Esposito-selected, and expansion-recovered quadratic obstructions, showing that vector-type torsion is forced-linear, pure tensor torsion is native-display linear but recovered in the certified comparison layer, and mixed vector--tensor torsion gives the first selected nonlinear boundary.