1. Filter words inside image_overlays (removes OCR from images)
2. Ghost filter: only remove single-char border artifacts, not multi-char
like (= which is real content
3. Skip first-row header detection for zones with image_overlays
(merged geometry creates artificial gaps)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Zone merging: content zones separated by box zones (images) are merged
into a single zone with image_overlays, so split tables reconnect.
Heading detection: after color annotation, rows where all words are
non-black and taller than 1.2x median are merged into spanning heading cells.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>