GCFT CDN-163: The Half That Wasn't — A Negative Linear-Response Result on the κ_c Coefficient

CDN-163 executes the derivation task pre-registered in CDN-162: whether the ½ in the coherence-coupling scaling law κ_c = −½·G·M_tot/v_typ follows from the Ξ kinetic structure. In 1D linear response around a spintessence background, the wake force of a moving gravitational source splits between the radial (δφ) and phase (δθ) channels as a continuous, damping-robust function of the anharmonicity Δ = V″(φ₀)−ω². The split runs from radial-dominated at the harmonic point (F_φ/F → 1 as v → 0, refuting the equipartition conjecture) to phase-dominated in the stiff limit, crossing ½ only at a tuned Δ* ≈ (4–8)ω², protected by no symmetry. Verdict: the ½ is not derived; by CDN-162's own criterion the coupling sector is phenomenology at toy level — the scaling law retains its empirical status (fixed by the LMC survival bound, the Venus kill, and the CDN-139 normalization) with a fitted coefficient. Claims discipline: only the channel split is asserted (damping-converged to 10⁻⁴); the drag magnitude and velocity law did not converge in the retarded limit, so the v_r-linearity of a_coh is flagged as assumed rather than derived. Salvage: the split is a clean monotone diagnostic of potential stiffness, with a labeled conjecture connecting stiff-environment phase-channel wakes to the compactness-gated sector. Remaining derivation routes: 3D wake integral, self-gravitating wake, time-domain radiation boundary conditions. Solver script, results JSON, and figure included. By Nicky Hacquier (Aporion Dynamics) — part of the General Coherence Field Theory research chain, Project Aporion; follows CDN-162 (DOI 10.5281/zenodo.20621964).