CDN-264: The SPARC Fit — GCFT Computational Discovery Note

Fits GCFT coupling parameters (κ_cl, a_t, γ) directly to the SPARC Radial Acceleration Relation (14 bins, 2630 data points, 153 galaxies). Best-fit: κ_cl=0.210, a_t/a₀=2.20, γ=0.76 — radically different from the dSph-calibrated CDN-258 values. Functional form marginally survives kill condition (RMS 0.046 ≤ 0.05 dex) but remains 2.4× worse than MOND simple. Cross-check against 22 dwarf spheroidals: 0/22 within 20% at any parameter set, with predicted velocity dispersions 15–50× too low. Joint optimization finds no connecting valley between galaxy-RAR and dSph parameter space. Two-sector coupling definitively confirmed. CDN-265 pre-registered for alternative functional forms.