CDN-228: Rotation Curves Without Halos

CDN-228 tests the first gate of the GCFT dark-matter-resolution arc using public SPARC rotation-curve mass models. A single baryon-tethered fixed response kernel is trained on half of the quality-1/2 galaxies and tested on the held-out half, with no per-galaxy dark halos. The fitted global scale is g_dagger = 1.141e-10 m/s^2. Held-out RMS fractional velocity error improves from 0.437 for baryons alone to 0.235 for the fixed response. The paper explicitly limits the result: this is rotation-support evidence, not a final GCFT derivation and not a lensing, cluster, growth, or CMB solution.