Single-Action Recovery of an Electron-Like Packet and Near-Electron Rest-Energy Scale in the ECSM Framework

This paper presents the V21b stage of the ECSM electron-like packet programme. Earlier stages established an inherited electron-like packet scaffold, a finite dimensionless rest-energy minimum, a physical scale-closure target, and a pre-target stiffness/action exponent that mapped the dimensionless packet energy close to the observed electron rest energy. The V21 stage attempted an all-or-nothing derivation from a single medium-action ledger but failed to recover the V17 rest-energy minimum and near-electron mass scale simultaneously. V21b is the corrected recovery stage. It restores the inherited V17 rest-energy minimum as a single recovered action while preserving the electron-like occupation branch, finite shell closure sequence, and recovered alpha/beta response algebra. The recovered action gives R_star = 4.057953270393597, E_star = -0.27637139084338974, and curvature = 0.03191359462708962, matching the V17 handoff to numerical precision. From the same recovered-action ledger, V21b regenerates the stiffness/action exponent p_action = 10.210030664542186 before comparison with the electron target. Under the same Planck-alpha dimensional audit used in V20, this gives Ephys = 514.0698767738036 keV, within approximately 0.601 percent of the electron rest-energy target. This result is deliberately framed as a strong recovery result, not a completed QED derivation. The construction does not insert 511 keV, does not solve p, xi, or tau from the electron mass, and does not claim radiative corrections, scattering amplitudes, or full field-theoretic electron self-energy. It shows that ECSM can recover an inherited electron-like packet minimum and regenerate a near-electron rest-energy scale from internal packet-closure quantities while retaining an explicit no-cheat audit and response-domain radius warning.