The Sharipov Smooth Quartic-Core Completion: An Action-Based Background and a Twenty-Three-Gate Validation Program

We present the Sharipov Smooth Quartic-Core Completion (SSQC), a new regular black hole solution in general relativity coupled to nonlinear electrodynamics. The metric is asymptotically Schwarzschild, has a fully analytic de Sitter-like core, and is sourced by an explicit magnetic NED Lagrangian with finite central density and radial pressure satisfying p_r = -ρ. A 23-gate validation program is formulated, covering action, smoothness, rotation, stability, EHT imaging, QNM spectra, and Bayesian inference. The algebraic Kerr-Newman-type rotation is tested and rejected; a field-equation slow-rotation construction is adopted instead. The minimal one-invariant NED source is shown to fail a constitutive hyperbolicity condition in the core, identifying the need for a two-invariant extension. This work establishes SSQC as a mathematically rigorous background and defines the verification framework required for a physically viable regular black hole.