v1 of N-engine compare (ADR-0065). Picks a spine engine (default: OCR-B) whose segmentation drives the column layout. For each spine segment, every other engine’s text is reachable via an inline “alternates” drawer — IoU-aligned for engines with bbox output, full-page projection for text-only engines. Stays readable with 5+ engines, unlike the side-by-side view at /ocr/compare.