Closes bf-3h10m. Verification: notes/bf-3h10m.md.
The fixture discovery functionality was already implemented in
tests/forms_integration.rs. All acceptance criteria PASS:
- Function discovers all .pdf files in tests/fixtures/forms/
- Test prints discovered fixture names when run
- Handles non-existent directory gracefully (empty vec)
- No compilation errors
Test execution: cargo test --test forms_integration test_discover_pdf_fixtures
Result: 1 passed, 0 failed
