COS45 — Calibration Theory Observable Indistinguishability Threshold and Stability Bounds

This document defines the calibration layer of COS45. The indistinguishability threshold τ_W is defined as an observable quantile over admissible transformations. τ_W is not a noise model. This document establishes:- the definition of τ_W- its dependence on the calibration protocol (W, n, q, K, T_adm)- stability bounds under perturbation (Weyl inequality)- certified decision zones based on ηₙ(W) All results are local and protocol-dependent. This document builds on:COS45 — Coherence Core (D0), DOI: 10.5281/zenodo.19595171