CI: test matrix across Python 3.10-3.13

[math280h]

pyproject.toml declares requires-python = ">=3.10", but the test workflow runs on a single default Python version. Compatibility breakage on other supported versions would ship unnoticed.

Proposal: add a version matrix (3.10, 3.11, 3.12, 3.13) to .github/workflows/test.yaml via uv python install/setup-uv's python-version input. The integration and benchmark workflows can stay single-version.