Grand Cosmological Convergence: Hubble Tension, Sigma-8 Suppression, and Void Fraction as a Unified Pe-Lambda Boundary Layer

Derives the Hubble tension (ΔH₀=5.6 km/s/Mpc) and σ₈ suppression (0.749 vs DES Y3 0.745) from a single Buchert backreaction term Q₀=2359 (km/s/Mpc)² peaked at the Pe_Λ=1 boundary. Requires void expansion rates of 16.1%, consistent with SDSS/DESI void surveys. No dark sector, no new physics, zero free parameters beyond observed cosmic void fraction.