Corrected zig-zag scan positions from 4-15 to 6-17 (verified against standard JPEG zig-zag ordering). Fixed inverted HVS luminance reasoning to correctly explain that luminance is used because it isn't spatially subsampled by JPEG, not because of visual sensitivity. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>