When textbook authors wrap text within a cell (e.g. long German
translations), OCR treats each physical line as a separate row.
New _merge_wrapped_rows() detects this by checking if the primary
column (EN) is empty — indicating a continuation, not a new entry.
Handles: empty EN + DE text, empty EN + example text, parenthetical
continuations like "(bei)", triple wraps, comma-separated lists.
12 tests added covering all cases.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
