CDN-206: The Upper Neighbor Breaks

CDN-206 measures two fresh below-crossing source-side neighbors around the CDN-203 failure. The upper neighbor at delta=0.075 fails cleanly: eps_inf = 0.028420 against frozen source prediction 0.011132, signed error +0.017288, lambda_phase_leak = 0.693944, monotone theta series, and all velocity peaks interior. The lower neighbor at delta=0.065 remains tail-unresolved because its floor fit hits the lower bound after theta ≈ 60. The hidden-channel band is open on the upper side, but the source interval is not repaired.