Add discover_pdf_fixtures function to recursively find all PDF files in
tests/fixtures/forms/ directory using walkdir. Includes test that prints
discovered fixture names to stdout.
Acceptance criteria:
- walkdir is available in crates/pdftract-cli/Cargo.toml
- discover_pdf_fixtures function returns Vec<PathBuf> of discovered PDFs
- test_discover_pdf_fixtures runs and prints fixture names
- No compilation errors
Closes bf-1pxdm.
- Created tests/forms_integration.rs with basic test module structure
- Created tests/mod.rs to aggregate test modules
- Added module documentation for forms integration tests
- File compiles successfully with cargo test --test forms_integration
Acceptance criteria:
- tests/forms_integration.rs exists ✓
- tests/mod.rs includes the module declaration ✓
- cargo test --test forms_integration compiles ✓
- File has basic test module skeleton ✓
Closes bf-2y7uh
