Add project configuration, .gitignore and the package skeleton

pyproject.toml declares Python 3.13 or later, an empty runtime dependency list and
pytest, ruff and mypy as development tools. The package has constants.py, the one
place for constants, and a smoke test keeps the test run green.

Task: MIL-001#1
Task: MIL-001#2
Task: MIL-001#3

.gitignore

@@ -0,0 +1,100 @@
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Documentation builds (Doxygen writes to build/doxygen, see Doxyfile)
+docs/_build/
+doxygen_warnings.log
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# Environments
+.env
+.envrc
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Type checkers and linters
+.mypy_cache/
+.dmypy.json
+dmypy.json
+.pyre/
+.pytype/
+.ruff_cache/
+
+# IDEs and editors
+.idea/
+.vscode/
+*.swp
+*.swo
+.spyderproject
+.spyproject
+.ropeproject
+
+# Operating system files
+.DS_Store
+Thumbs.db
+desktop.ini