Implement the conformance test runner pattern that every SDK will
implement to validate against the shared test suite.
- Rust reference implementation (crates/pdftract-core/tests/conformance.rs)
* Full test suite loader and executor
* Comparison engine with min/max, string constraints, tolerances
* Skip logic for unsupported features and schema versions
* Report generation in JSON format
- CLI compare subcommand (crates/pdftract-cli/src/main.rs)
* pdftract compare - Compare actual vs expected with tolerances
* Cross-language comparison tool to avoid reimplementations
- Documentation (docs/conformance/sdk-contract.md)
* Complete pattern specification with pseudocode
* Per-language runner locations
* CI integration requirements
- Python reference stub (tests/python-conformance/test_conformance.py)
* Full pytest-based implementation following the pattern
Closes: pdftract-5omc
857f928732