ESSC v28: A Sparse Predictive Gate for Conversion Success in the Usable Galaxy Manifold

ESSC v28 develops a sparse predictive gate for conversion success within the usable galaxy manifold established in ESSC v27. The central result is that conversion success is not determined by peak-side baryon amplitude alone. Instead, it is organized by a compact joint gate whose dominant components are low location-side halo support, outward peak placement, and positive pre-transition spacing, canonically expressed through location_f_halo, peak_R_over_Rdisk, and d_loc_to_peak_rrd. Secondary modifiers include strict_prepeak_ratio, location_Vbar_kms, and peak_f_baryon. Repeated sparse validation yields a mean ROC AUC of about 0.905, balanced accuracy of about 0.816, and Brier score of about 0.137. The analysis also supports a finite-width conversion-band interpretation rather than a single sharp threshold, and a comparison with stacked HSC weak-lensing structure is included as external consistency. This work does not propose a new force law or replace direct dynamical modeling; its claim is narrower and operational: within the v27 usable manifold, conversion success is predictably organized by a sparse, stable, and interpretable structural gate.