V.R453 — DESI σ₈ Falsification Window

τ-prediction: (f·σ₈)_τ/(f·σ₈)_Λ ≈ 0.97, z-independent. DESI DR3 + Euclid DR1 at ~1% precision → decisive. Falsified if f·σ₈ agrees with ΛCDM at <1% or shows z-dependent departure.