NT16: Regime Analysis and Signal-Envelope Decomposition for the wᵦ = 11. 1991 Minimum

This note applies a regime-analysis framework to the ωᵦ = 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 ncrit separating resolvable from degenerate behaviour; (3) a candidate sector invariant — the harmonic amplitude ratio P (2ωᵦ) /P (ωᵦ) ∝ e⁴. 86 — independent of A₀ and φ; (4) a formal signal–envelope decomposition separating the oscillatory component from the smooth w₀wₐ 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.