CDN-252: The Three Surveys — eROSITA, ACT DR5, and F-Class Closure

Three simultaneous tests of the locked CDN-242 κ-proxy. (a) eROSITA DR1 cosmology subsample (5,012 clusters with real T_X, M_gas, D_COMB — richest vectors in the programme): PASS at M200 ≥ 0.5×10^14 M☉ (96.5% in-band, 0 cap violations); raw CONFLICT traced to 12 galaxy groups below the proxy's training floor. (b) ACT DR5 (4,195 SZ-selected clusters, Hilton+2021): PASS — 99.7% in-band, 0 cap violations, 97.37% closure — cleanest result in the programme. (c) F-class targeted search (333 relaxed massive eROSITA clusters): 0 F-class found; 332/333 are E-class. F-class is an artefact of the CDN-240 6-parameter proxy, eliminated by the CDN-242 7-term quadratic-λ correction. Taxonomy reduced from E/S/P/F to E/S/P. Combined: the proxy passes on ~9,700 clusters across four independent surveys spanning lensing, SZ, and X-ray selection from z=0.04 to z=1.91. Includes execution script, full per-cluster results JSON, and Art Edition.