nx_intra_pred_gate.nx

nx_intra_pred_gate.nx -- MEASURES the directional-intra-prediction lever on REAL content before any core-codec change. On the real 768x768 H.264-decoded luma frame, for every interior 4x4 block, compare the residual SAD of DC-only prediction (what the codec does today) vs the best of {DC, vertical, horizontal, diagonal-down-right}. The reduction is how much smaller the residual that must be entropy-coded becomes -- the first-order size of the intra win. HONEST: predicts from ORIGINAL neighbor samples (an upper bound; a real codec predicts from reconstructed neighbors), so this bounds the available gain rather than the exact post-quant bitrate. Reusable lib nx_intra_pred is the org.