test: add pytest suite for core modules

- Add pytest dependency and config to pyproject.toml
- Test project_root: env var priority, fallback, directory creation
- Test CLI: help, version, subcommands, default behavior, options

pyproject.toml

@@ -11,6 +11,13 @@ dependencies = [
 [project.scripts]
 myclaude = "myclaude.cli:cli"
 
+[dependency-groups]
+dev = ["pytest>=8.0"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+python_files = ["test_*.py"]
+
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"