_codec_bench_med.nx

_codec_bench_med.nx -- X-CDC-FRAME-LZ-001 rung: sovereign-PREDICTOR PNG-style head-to-head. Measured finding (X-BENCH-CODEC-002): fc loses to PNG-class because it has no LZ stage. But fc owns the MED (LOCO-I/JPEG-LS) predictor, while PNG offers only fixed filters (None/Sub/Up/Avg/ Paeth). This rung ISOLATES PREDICTOR QUALITY: feed BOTH the MED residual and the PNG-Sub residual to the SAME sovereign deflate, on the SAME corpus. MED+deflate < Sub+deflate => the MED prefilter EXCEEDS PNG's Sub filter (no-wave: only the prefilter differs; both sides our deflate; both sovereign). No-false-green: each frame's MED+deflate pipeline is end-to-end round-trip verified (MED-residual -> deflate -> our inflate -> un-MED == original), plus a tamper check that MUST fail. GREEN iff round-trip exact on all 5 AND tamper detected; the exceed COUNT is reported, never forced.