nx_imgsig_gate.nx

nx_imgsig_gate.nx -- referee for the unified visual signature (nx_imgsig = visdesc + colordesc). PROVES the COMBINATION beats either component alone, on a 2x2 structure x color corpus where each component is individually ambiguous: classes = {H-stripes RED, H-stripes GREEN, V-stripes RED, V-stripes GREEN}, 4 instances each. - visdesc alone (structure/tone on gray) CONFUSES H-red vs H-green (same structure) -> lower P@3. - colordesc alone (chroma) CONFUSES H-red vs V-red (same color) -> lower P@3. - imgsig (both) separates all four. row1 imgsig retrieval P@3 strong (>=850 permil). row2 imgsig P@3 > visdesc-only P@3 (color disambiguates what structure cannot) [measured] row3 imgsig P@3 > colordesc-only P@3 (structure disambiguates what color cannot) [measured] row4 DETERMINISM: same image twice -> identical signature (L1 == 0). row5 SEPARATION: cross-class imgsig L1 >> same-class. GREEN iff 5/5. Durable verdict -> knowledge/status/imgsig_gate.log. license_tier: ORIGINAL