Λ Constant, w Evolving: A Topological Resolution

Mode Identity Theory holds Λ fixed by construction, yet DESI DR2 reports 2.8-4.2σ evidence that the dark energy equation of state w evolves with redshift. This paper resolves the tension: the cosmic standing wave Ψ(t) = cos(t/2) modulates the dark energy surface mode Ω_Λ^bare, producing apparent w(z) evolution when observers fit constant-Λ distances with fluid-based templates. The surface-mode coupling is invisible to the CMB by construction (Ω_Λ^bare/E²(z*) ~ 10⁻⁹ at recombination) while preserving the full BAO and supernova signatures at low redshift. Friedmann inversion proves w_eff(z) > -1 at all redshifts; the phantom crossing is a CPL template artifact at z ≈ 0.66. Tested against DESI DR2 BAO data, Pantheon+ supernovae, and a Planck-calibrated CMB ruler prior, MIT with locked parameters (δ = -1.06 rad, ε = 0.255) achieves ΔAIC = -2.1 over ΛCDM. Profiling the coupling amplitude yields ε = 0.16 with Δχ² = -7.9 (ΔAIC = -5.9 at k = 3). All predictions registered prior to Euclid DR1. Latest derivation of this paper can be found at github.com/dark-energy v6 update: coupling target changed from total-H modulation to surface-mode coupling on Ω_Λ^bare, resolving CMB tension (old ansatz imprinted ~13% distortion at recombination; new coupling contributes ~10⁻⁹ to E² there). ε calibration now numerical inject-and-recover (0.255, down from analytic 0.263). w_eff > -1 proof simplified: single sin θ term, sign unambiguous. Data scope expanded from BAO-only to combined BAO + Pantheon+ + Planck H₀r_d prior. Statistical preference strengthened (ΔAIC = -2.1 over ΛCDM locked, -5.9 profiled). Core predictions and locked parameters unchanged.