A Model-Excess Compactness Framework for the Three-Dimensional Navier–Stokes Regularity Problem

This manuscript presents a conditional proof framework for studying possible finite-time singularity formation in the three-dimensional incompressible Navier–Stokes equations. The approach compares rescaled solutions against smooth local Navier–Stokes model profiles and analyzes the remaining excess through localized energy, diffusion, and compactness estimates. The work is intended as a structured research framework and conditional closure theorem. It identifies the main estimates and proof obligations required for a referee-grade regularity argument, especially the cross-scale compactness absorption mechanism. It does not claim an unconditional resolution of the Navier–Stokes regularity problem unless the stated local estimates are verified in full detail.