All acceptance criteria PASS. The extract() function was already
implemented in crates/pdftract-py/src/extract.rs with:
- Strict kwarg validation (ALLOWED_KWARGS list)
- GIL release via py.allow_threads during extraction
- Python dict conversion via pythonize::pythonize
- Error mapping to PdftractError hierarchy
See notes/pdftract-41lbg.md for detailed verification.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
