Add wheel building CI workflow

[jc-macdonald]

Add a GitHub Actions workflow to build wheels on PR and push events.

Scope

• Create .github/workflows/build.yaml (or extend ci.yaml)
• Build sdist + wheel using python -m build (or uv build)
• Upload wheel as artifact for testing
• Matrix: Python 3.11, 3.12, 3.13 minimum
• Consider cibuildwheel if C extensions are added in future

Related

• Add PyPI publish workflow #37 (PyPI publish workflow consumes these artifacts)

[TimothyWillard]

#57