uv run eest make test runs correctly, but the generated test module is not correctly formatted.

From the copilot review:

The code now references AppConfig().ROOT_DIR.parent instead of AppConfig().ROOT_DIR to find pyproject.toml. This change suggests the ROOT_DIR definition may have changed during the refactor. Verify that ROOT_DIR still points to the correct location (packages/testing/src/execution_testing) and document why .parent is now needed.

        # Call ruff to format the file
        # AppConfig().ROOT_DIR points to 'packages/testing/src/execution_testing'.
        # The project's pyproject.toml is located in the parent directory: 'packages/testing/src'.
        # Therefore, we use .parent to correctly reference the config file.

Originally posted by @Copilot in #1654 (comment)