Address 5 weaknesses found via ground-truth comparison on session df3548d1:
- Add column_ignore for edge columns with < 3 words (margin detection)
- Absorb tiny clusters (< 5% width) into neighbors post-merge
- Restrict page_ref to left 35% of content area across all 3 levels
- Loosen marker thresholds (width < 6%, words <= 15) and add strong
marker score for very narrow non-edge columns (< 4%)
- Add EN/DE position tiebreaker when language signals are both weak
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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