Nuclear Mass Operator Map and Shell Closure Diagnostic Validation (SBQM Paper 3)

This archive documents SBQM Paper 3: a conservative status freeze of a nuclear-mass operator-map and shell-closure diagnostic validation programme. The package supports two defensible claims. First, S2core is externally supported as a diagnostic low-energy nuclear-mass operator map under the reported no-leakage validation protocol. Second, S3mass = S2core + Eclosure is empirically supported as a no-mass-fit, gap-selective shell-closure extension under a finite-well/Dirac-like effective ordering. The archive deliberately does not claim a first-principles derivation of nuclear structure. It does not validate broader S3/H4 geometry, MG, kappa, 600-cell assumptions, or hadronic mass-algebra claims. Those remain outside the scope of this paper. Included materials provide the manuscript, frozen validation summaries, closure-test registers, reproducibility metadata, and claim-boundary documentation. The package is intended as a reproducible diagnostic status record rather than a final theory paper.