CoreLumen Stage VI : Robustness and Structural Stability of the Response Framework

This document constitutes Stage VI of the CoreLumen Stage Series (v1.0). Stage VI provides a bounded robustness verification of the finalizedStage II–V framework within the quasi-static (QS) domain.No new theoretical structures are introduced. Controlled perturbations of kinetic normalization, effective mass,and background expansion are examined to test structural survival.Within the defined perturbative envelope and QS trust region,no instability, pole generation, algebraic breakdown,or loss of A_eff locking is detected. All propagation-sector constraints remain enforced:c_T = 1, c_s^2 > 0, Z_theta > 0. Breakdown occurs only at the expected QS boundary(ε_QS → O(1)), corresponding to the limitation of thequasi-static approximation itself. Stage VI records structural stability verificationwithin the effective-field validity regime.