GCFT CDN-165: No Refuge in Geometry — The 3D Wake Integral Reproduces the 1D Verdict

CDN-165 closes the first of CDN-163's remaining derivation routes for the ½ coefficient in the κ_c scaling law. The 3D steady-state wake integral, computed via exact cylindrical reduction to a (k_x, k_⊥) mode solve, reproduces the 1D verdict: the radial-channel share at the harmonic point is 0.94 (v=0.3; damping-converged to ±0.002, stable under 2× resolution), descending monotonically through ½ only at a tuned Δ* ≈ (4–16)ω². Three-dimensional geometry does not produce the ½; theory debt D1 stands and the coupling sector remains phenomenology. Claims discipline as in CDN-163: only the channel split is asserted. Remaining routes: the self-gravitating wake and time-domain/nonlinear treatment with radiation boundary conditions — the latter also the only route that can decide debt D2 (the v_r-linearity). Solver script, results JSON, and figure included. By Nicky Hacquier (Aporion Dynamics) — Project Aporion; follows CDN-164 (DOI 10.5281/zenodo.20622292).