Fix half-height rows caused by tall special characters (brackets, IPA
symbols) being split into separate line clusters:
- Group words by vertical CENTER instead of TOP position, so tall
characters on the same line stay in one cluster
- Filter outlier-height words (>2× median) when computing letter_h
so brackets/IPA don't skew the row height
- Merge clusters closer than 0.4× median word height (definitely
same text line despite slight center differences)
- Increased y_tolerance from 0.5× to 0.6× median word height
- Enhanced logging with cluster merge count and row height range
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
97d4355aa9