refactor(paths): v3 design - explicit initialize_paths + frozen PathsConfig singleton

sloppy.py

@@ -42,9 +42,8 @@ args: argparse.Namespace = argparse.Namespace()  # type: ignore[assignment]
 if __name__ == "__main__":
  args = parser.parse_args()
  from pathlib import Path
- from src.paths import set_config_override
- if args.config:
-  set_config_override(Path(args.config).resolve())
+ from src.paths import initialize_paths
+ initialize_paths(Path(args.config).resolve() if args.config else None)
  if args.web_host is not None:
   with startup_profiler.phase("web_host_imports"):
    from imgui_bundle import hello_imgui