Summary

• migrate string enum classes to StrEnum so current Ruff UP042 checks pass without suppressions
• normalize Ruff formatting drift and fix the Sphinx title underline warning
• harden tuner-report tests to use sys.executable for subprocess runs
• update release-prep planning artifacts and changelog for the v1.0.0 GA preflight gate

Closes #15.

Verification

• .venv/bin/ruff format src tests
• .venv/bin/ruff check src tests
• .venv/bin/mypy src
• .venv/bin/pytest tests/test_analyze_tuner_reports.py
• .venv/bin/pytest
• .venv/bin/pre-commit run --all-files
• PANDOC_DIR=$(...) PATH="$PANDOC_DIR:$PATH" .venv/bin/sphinx-build -b html docs _build/html -W

Full pytest result: 299 passed, 210 skipped, 61 warnings.
Sphinx required local Pandoc; I provided it through pypandoc_binary for local verification. CI installs Pandoc via apt before docs build.