GCFT CDN-160: The Magellanic Stream Test — Executing the CDN-157 Prediction Against the HI4PI High-Velocity Sky

CDN-160 executes the only pre-registered GCFT test available without a future data release: the CDN-157 Magellanic Stream asymmetry prediction. Using the HI4PI-derived all-sky high-velocity-cloud maps of Westmeier (2018, MNRAS 474, 289) in Magellanic coordinates, we measure the trailing/leading mean HI column-density ratio of the Stream. The result is 1. 68 1. 35–2. 08 in the baseline aperture (|BMS| ≤ 15°) and 2. 27 1. 83–2. 77 in the narrow band (|BMS| ≤ 10°, stable under a velocity-coherence filter) — a range that brackets both the ΛCDM expectation (~2. 0) and the GCFT prediction (~2. 3). Neither kill nor confirmation: the band-width systematic (±0. 3) equals the predicted signal. The trailing tip is recovered at LMS ≈ −140°, consistent with Nidever et al. (2010) ; the stream-extent prediction cannot be adjudicated because the leading side is confusion-limited. The note names three systematics (kinematic blocking, membership ambiguity, baseline softness) and pre-registers the cube-grade repeat: primary aperture |BMS| ≤ 10° with velocity filter, kill if T/L < 1. 9, supportive if ≥ 2. 2 with a matched hydro baseline. Analysis script, results JSON, and figure included. Part of the General Coherence Field Theory research chain (Project Aporion) ; follows Part IV: The Falsification Era (CDN-150–159).