VMAF-NEG enhancement-gain checker

A dependency-light Python script (standard library only) that reads a libvmaf JSON log holding both the default and NEG VMAF scores (or two separate logs), reports each score pooled four ways (mean, harmonic mean, 5th percentile, single worst frame), computes the per-frame and overall enhancement-gain gap (default minus NEG), flags any clip whose gap is large enough that the default score is riding on enhancement rather than compression, and warns on any frame scoring above 100. Includes the cur