Add package artifact smoke CI job and finalize changelog

[srichs]

Motivation

• Implement release checklist items to validate built distribution artifacts and ensure entrypoint smoke tests are part of CI.
• Reconcile changelog state so completed work is recorded under a dated 0.1.0 release and a fresh Unreleased section is present.

Description

• Add a package-smoke job to .github/workflows/ci.yml that runs python -m build, installs the built wheel with python -m pip install --force-reinstall dist/*.whl, and smoke-tests both devr --version and python -m devr --version.
• Update CHANGELOG.md to add an empty Unreleased section and move existing completed entries into ## [0.1.0] - 2026-02-17.

Testing

• Ran the test suite with pytest -q which passed: 93 passed.
• No automated test failures were observed after the changes.

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Codex Task