fix(packaging): stop including legacy pkgmgr.installers package

- Restrict setuptools package discovery to src/ (pkgmgr* only)
- Drop config/ as a Python package mapping (keep config as plain data dir)
- Remove config_defaults fallback paths and use config/ exclusively
- Add unit + integration tests for defaults.yaml loading and CLI update copying

https://chatgpt.com/share/6947e74f-573c-800f-b93d-5ed341fcd1a3

src/pkgmgr/cli/commands/config.py

@@ -42,9 +42,7 @@ def _find_defaults_source_dir() -> Optional[str]:
     project root that contains default config files.
 
     Preferred locations (in dieser Reihenfolge):
-      - <pkg_root>/config_defaults
       - <pkg_root>/config
-      - <project_root>/config_defaults
       - <project_root>/config
     """
     import pkgmgr  # local import to avoid circular deps
@@ -53,9 +51,7 @@ def _find_defaults_source_dir() -> Optional[str]:
     project_root = pkg_root.parent
 
     candidates = [
-        pkg_root / "config_defaults",
         pkg_root / "config",
-        project_root / "config_defaults",
         project_root / "config",
     ]
     for cand in candidates:
@@ -73,7 +69,7 @@ def _update_default_configs(user_config_path: str) -> None:
     source_dir = _find_defaults_source_dir()
     if not source_dir:
         print(
-            "[WARN] No config_defaults or config directory found in "
+            "[WARN] No config directory found in "
             "pkgmgr installation. Nothing to update."
         )
         return

src/pkgmgr/core/config/load.py

@@ -14,9 +14,7 @@ Layering rules:
    - Falls dort keine passenden Dateien existieren, wird auf die im
      Paket / Projekt mitgelieferten Config-Verzeichnisse zurückgegriffen:
 
-         <pkg_root>/config_defaults
          <pkg_root>/config
-         <project_root>/config_defaults
          <project_root>/config
 
      Dabei werden ebenfalls alle *.yml/*.yaml als Layer geladen.
@@ -218,7 +216,6 @@ def _load_defaults_from_package_or_project() -> Dict[str, Any]:
     # Candidate config dirs
     candidates = []
     for root in roots:
-        candidates.append(root / "config_defaults")
         candidates.append(root / "config")
 
     for cand in candidates: