Add GitHub Actions workflows for CI and PyPI publishing

[Copilot]

Adds automated testing and package publishing workflows following the packaging infrastructure added in the previous commit.

Workflows

CI (.github/workflows/ci.yml)

• Matrix testing: Python 3.8-3.12 × Ubuntu/macOS/Windows
• Linting (flake8), formatting (black), type checking (mypy)
• Test execution with coverage upload to Codecov

Publish (.github/workflows/publish.yml)

• Builds source and wheel distributions
• Publishes to TestPyPI (manual) or PyPI (on release)
• Uses Trusted Publishing (OIDC) - no API tokens required
• Supports manual dispatch with boolean flag for test vs production

Both workflows enforce explicit GITHUB_TOKEN permissions per security best practices.

Setup Required

Configure Trusted Publishers on PyPI/TestPyPI:

• Project: python-schema-manager
• Owner: hapticPaper
• Workflow: publish.yml
• Environments: pypi and testpypi

See .github/workflows/README.md for detailed setup instructions.

Original prompt

ok, i merged those and added the packaging stuff you left out. now create the git actions files to create the pip packages

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