Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Replace setup.py/setup.cfg/requirements.txt with pyproject.toml
- Add uv to .mise.toml managed tools, remove manual venv config
- Update CI workflow to use astral-sh/setup-uv and uv commands
- Update publish workflow to use uv build/publish with OIDC trusted publishers
- Add AGENTS.md with updated setup/test instructions
- Add uv.lock to .gitignore (library, not application)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Switch from [project.optional-dependencies] to [dependency-groups]
  so that `uv sync --dev` correctly installs dev dependencies
- Replace flake8 with ruff in the CI workflow
- Remove dead `found_block` variables in resolver.py caught by ruff

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>