FCI v4.0 Phase Boundary Sweep — Critical Coupling Thresholds in Regenerative Propagation Collapse

This paper presents a focused phase-boundary analysis of the Follicular Coherence Index (FCI) computational twin to investigate whether regenerative decline emerges gradually or through nonlinear propagation collapse. By sweeping coupling strength and stochastic noise across a coupled follicular lattice, the study identifies a sharp logistic transition governing regenerative coherence. The results demonstrate that coupling strength exerts substantially greater control over regenerative propagation than noise amplitude alone, and that restoring coupling can partially rescue regenerative competence even under persistently aged conditions. The work introduces recoverable and nonrecoverable propagation regions, defines a modeled critical coupling threshold, and extends the broader Coherence Threshold Hypothesis into quantitative phase-transition analysis.