nx_vmotion_gate.nx

nx_vmotion_gate.nx -- proves + MEASURES sovereign motion compensation (nx_vmotion), the rung that beats plain tile-delta the way VP8/H.264 do. Native nx_cc->nxasm, no node. 1) PAN exceed: a frame shifted by (3,2) -> tile-delta sees the block as fully changed (huge SAD), motion search finds the shift (MV) with ~0 residual -> measured: motion-comp << tile-delta on motion 2) MV correctness: the found vector equals the true shift (negated) 3) lossless reconstruct: predicted-at-MV + residual == the cur block 4) static block: cur==prev -> MV=(0,0), SAD=0 5) honest limit (neg): a noisy block with no match -> SAD stays high (motion comp isn't magic -> intra fallback) license_tier: ORIGINAL