Minimal Disformal Ansatz and Two-Scale Constraints for the Radial Acceleration Relation in RCD

We construct the simplest effective disformal profile h(g_bar) that achieves the observed RAR slope at a_0 within the spherical QS proxy. Combined with the conformal S3 kinetic function, a two-parameter ramp-and-cut profile (h_0=0.40, g_s=2a_0) yields slope 0.608 at a_0 (observed ~0.6), boost 1.584, and Cassini safety (h~10^-15 at Saturn). The existence window is h_0 in [0.38, 0.44].