1. Syllable "Original" (auto) mode: only normalize cells that already
have | from OCR — don't add new syllable marks via pyphen to words
without printed dividers on the original scan.
2. Syllable "Aus" (none) mode: strip residual | chars from OCR text
so cells display clean (e.g. "Zel|le" → "Zelle").
3. Heading detection: add text length guard in single-cell heuristic —
words > 4 alpha chars starting lowercase (like "zentral") are regular
vocabulary, not section headings.
4. Word-gap merge: new merge_word_gaps_in_zones() step with relaxed
threshold (6 chars) fixes OCR splits like "zerknit tert" → "zerknittert".
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>