Three Resolutions Under Fire + The Virial Threshold: GCFT Coupling Sector Stress Test [CDN-141 + CDN-142 Bundle]

CDN-140 established a 4×10²¹ gap between the Venus ephemeris upper bound on GCFT coherence coupling (κ_c ≤ 2.4×10⁻¹⁷ kpc² Gyr⁻¹) and the Andromeda flyby signal (κ_c ~ 5×10⁴ kpc² Gyr⁻¹), ruling out scale-invariant coupling as a universal constant. This bundle contains two sequential stress-test papers. CDN-141 runs Monte Carlo leapfrog simulations (N = 50,000) of the MW–Andromeda system under three candidate resolutions: Yukawa radial turn-on, mass-ratio power-law scaling, and local density screening. The Yukawa variant is analytically self-falsified (requires λ_c > 2×10²⁶ kpc, sixteen orders of magnitude beyond the Hubble radius). The mass-ratio variant passes Solar System and pulsar bounds but fails the LMC infall constraint at all viable exponents. Density screening survives all tests with ΔP = +25% flyby enhancement. CDN-142 then constrains the surviving density screening mechanism. Integrating LMC orbital dynamics under an NFW halo profile, the viable screening threshold is identified as ρ_crit ∈ [10³, 10⁴] M☉ kpc⁻³, placing the coupling activation radius at 260–387 kpc — coincident with the Milky Way virial boundary without parameter tuning. The mechanism is structurally analogous to chameleon/symmetron screening. A five-test falsification roadmap is provided. Simulation scripts included as appendix.