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 (|B_MS| ≤ 15°) and 2.27 [1.83–2.77] in the narrow band (|B_MS| ≤ 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 L_MS ≈ −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 |B_MS| ≤ 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).