chore(release): bump version to 1.3.18

Bump the package version to 1.3.18, upgrade dependencies,
consolidate module exports, add a unit test suite, and document
all changes.

- Bump package version to 1.3.18 in pyproject.toml
- Upgrade pydantic-settings to 2.14.2 and pyright to 1.1.411
- Consolidate package exports in mdrsclient/__init__.py
- Add a comprehensive unit test suite in tests/test_commands.py
- Document testing execution and add full history in CHANGELOG.md

mdrsclient/__init__.py

@@ -1,7 +1,4 @@
 from mdrsclient.__version__ import __version__
-
-__all__ = ["__version__"]
-
 from mdrsclient.client import MdrsClient
 
-__all__ = ["MdrsClient"]
+__all__ = ["__version__", "MdrsClient"]