Stationary Response-Energy Mass Selection in Natural Physics: A Unified Mass Architecture for Leptons and Nucleons

This paper develops a stationary response-energy account of rest-mass selection within Natural Physics. A conservative common-complex localization branch is shown to admit nonzero finite-energy, orbitally stable stationary states, providing a mass-independent existence basis before numerical spectral selection. The finite-response registry then supplies a branch-closed charged-family construction and a common mass scale from which numerical values for the principal massive constituents of ordinary matter are obtained. The resulting forward values are (0.5106758) MeV for the electron, (938.213785460) MeV for the proton, and (939.531816413) MeV for the neutron, with the nucleon values lying within a few (10^{-5}) fractionally of experiment. The same construction also generates the charged-lepton family hierarchy. The result is therefore a candidate unified stationary mass architecture spanning leptons and nucleons from one finite-response grammar and rest-energy map. The nucleon composite and charge-doublet identifications remain explicitly conditional; atomic binding and many-body mass defects are not claimed to be derived here.