GCFT CDN-175: Sigma-Universality of the Acoustic Floor — Floor Position cₛ (Δ) Confirmed Universal, Convergence Rate Governed by Δ·σ², σ∈8, 16, 32

CDN-175 (Coherence Domain Nucleation audit note 175) in the General Coherence Field Theory (GCFT) series, Project Aporion. Pre-registered in CDN-174. Tests σ-universality of the acoustic floor v* (Δ) → cₛ (Δ) = √ (Δ/ (Δ+4) ) established in CDN-173/174 at σ=16. Runs 35 simulation pairs at σ∈8, 32 using the T=20σ/cₛ protocol, Δ∈0. 040, 0. 060, 0. 080, 0. 100. Finding: the floor POSITION cₛ (Δ) is confirmed σ-universal. The residual excess ε = v*/cₛ − 1 at finite T is governed by the dimensionless ratio ξ = Δ/Δc (σ) = Δ·σ²: σ=8 (ξ~3–6) gives ε~9–18%; σ=32 (ξ~60–100) gives ε~−0. 5%, essentially at the floor. All three σ values collapse onto a single ε (ξ) curve. The two-parameter convergence law ε (ξ, T/τₗocal) is pre-registered for CDN-176. Lock code: CDN175SIGMADEPENDENTINVESTIGATEFLOORUNIVERSALCONVRATEDELTASIGMA2 Includes: simulation script (gcftcdn175ₛigmaᵤniversality. py), checkpoint JSON, results JSON, 3-panel figure, TeX note, Art Edition PDF.