Summary

• add a release prep script that bumps pyproject/service versions, rolls Unreleased changelog notes into a dated version section, seeds a fresh Unreleased section, and refreshes uv.lock
• pre-seed the current Unreleased changelog section with all supported headers
• add focused tests for changelog finalization and version replacement

Testing

• uv run pytest tests/test_prepare_release.py -q
• uv run ruff check scripts/init.py scripts/prepare_release.py tests/test_prepare_release.py
• env UV_CACHE_DIR=/private/tmp/sdk-python-uv-cache uv run mypy --namespace-packages --check-untyped-defs scripts/prepare_release.py tests/test_prepare_release.py
• uv run pyright scripts/prepare_release.py tests/test_prepare_release.py
• python3 .github/scripts/release_verify.py changelog-notes --version 1.29.0 --output /tmp/sdk-python-release-notes.md