rigour: add build-rigour.yml for riscv64 wheels

[luhenry]

• Package: rigour
• Version: 2.4.1
• Source: https://github.com/opensanctions/rigour
• Docs: https://rigour.followthemoney.tech/

Compiles a Rust/PyO3 extension for financial-crime domain data validation and normalization (names, addresses, IDs, phonetics). Upstream publishes no riscv64 wheel.

Mirrors upstream's linux/sdist jobs of build.yml.

Differs from upstream

• Builds from checkout, no separate sdist job - Cargo.lock is committed, so there's nothing to protect against.
• dnf install -y libicu-devel in before-all - normality (a runtime dep) hard-requires pyicu, which has no riscv64 wheel; the package lives outside EPEL.

Matrix: cp310-cp314, no cp314t - upstream builds no free-threaded wheel and pyo3's extension-module feature carries no abi3, so the matrix mirrors upstream's own five interpreters.

Testing

• same as upstream's pytest suite, minus the lint/typecheck/data-freshness steps (build-only concerns)
• test-sources stages tests/ alone so the checkout's own rigour/ package doesn't shadow the installed wheel
• adds typing_extensions to test-requires - rigour/ids/__init__.py imports it directly but it's missing from [project].dependencies
• cp310 only: deselects two test_dates.py cases - they hardcode a Z-suffixed/colonless-offset timestamp that only datetime.fromisoformat parses from Python 3.11 onward

License: OK

Built on cp312; 535 passed.