partially address --root CLI argument handling

- fix places where `get_config()` is being called at import time rather
  than at run time.

- add regression test for import time get_config() calling.

tests/test_config.py

@@ -1,3 +1,4 @@
+import sys
 from pathlib import Path
 from tempfile import TemporaryDirectory
 from typing import Any
@@ -7,6 +8,7 @@ from omegaconf import OmegaConf
 from pydantic import ValidationError
 
 from invokeai.app.services.config.config_default import InvokeAIAppConfig, get_config, load_and_migrate_config
+from invokeai.frontend.cli.arg_parser import InvokeAIArgs
 
 v4_config = """
 schema_version: 4
@@ -76,6 +78,13 @@ def test_read_config_from_file(tmp_path: Path):
     assert config.port == 8080
 
 
+def test_arg_parsing():
+    sys.argv = ["test_config.py", "--root", "/tmp"]
+    InvokeAIArgs.parse_args()
+    config = get_config()
+    assert config.root_path == Path("/tmp")
+
+
 def test_migrate_v3_config_from_file(tmp_path: Path):
     """Test reading configuration from a file."""
     temp_config_file = tmp_path / "temp_invokeai.yaml"