CDN-207: The Edge Flickers

CDN-207 tests the upper edge of the source-side hidden-channel band with a fresh delta=0.0775 run and a late-tail extension of the old delta=0.080 tight pass to theta≈60. The edge is not cleanly pinned. Delta=0.0775 is a full-window tight pass with source error +0.005609, but late-window fits miss by about 0.0004-0.0005 beyond tolerance. Delta=0.080 becomes a full-window tiny fail with source error -0.006998, while its late-window fits pass. The paid result is a window-sensitive transition zone, not a selector boundary.