NT16: Regime Analysis and Signal-Envelope Decomposition for the w_z = 11.1991 Minimum

This note applies a regime-analysis framework to the ω_z = 11.1991 minimum of the COCM oscillatory parametrisation. The analysis has six components: (1) separation of the base law from its regime correction; (2) identification of a regime boundary n_crit separating resolvable from degenerate behaviour; (3) a candidate sector invariant — the harmonic amplitude ratio P(2ω_z)/P(ω_z) ∝ e^4.86 — independent of A_0 and φ; (4) a formal signal–envelope decomposition separating the oscillatory component from the smooth w_0w_a envelope; (5) convergent robustness tests from five independent routes; and (6) an explicit scope-and-limits section. The analysis does not propose a new physical law; it provides a methodological framework for interpreting existing results and identifying what DESI DR3 must resolve.