feat(sdk): add addon registry wrappers to kindred_sdk (#384)

New module kindred_sdk/registry.py wraps FreeCAD.KindredAddons so
addons use a stable SDK import instead of reaching into FreeCAD
internals directly.

New public API:
- sdk.is_addon_loaded(name) — boolean check
- sdk.addon_version(name) — version string or None
- sdk.loaded_addons() — list of loaded addon names in load order

mods/sdk/kindred_sdk/__init__.py

@@ -21,6 +21,7 @@ from kindred_sdk.origin import (
     set_active_origin,
     unregister_origin,
 )
+from kindred_sdk.registry import addon_version, is_addon_loaded, loaded_addons
 from kindred_sdk.statusbar import register_status_widget
 from kindred_sdk.theme import get_theme_tokens, load_palette
 from kindred_sdk.toolbar import register_toolbar
@@ -29,14 +30,17 @@ from kindred_sdk.version import SDK_VERSION
 __all__ = [
     "SDK_VERSION",
     "active_origin",
+    "addon_version",
     "create_version",
     "current_context",
     "freecad_version",
     "get_origin",
     "get_theme_tokens",
     "inject_commands",
+    "is_addon_loaded",
     "list_origins",
     "load_palette",
+    "loaded_addons",
     "refresh_context",
     "register_command",
     "register_context",

mods/sdk/kindred_sdk/registry.py

@@ -0,0 +1,53 @@
+# kindred_sdk.registry — addon registry queries
+#
+# Thin wrappers around FreeCAD.KindredAddons (AddonRegistry) so addons
+# use a stable SDK import instead of reaching into FreeCAD internals.
+
+import FreeCAD
+
+
+def _get_registry():
+    """Return the AddonRegistry singleton, or None if not yet initialized."""
+    return getattr(FreeCAD, "KindredAddons", None)
+
+
+def is_addon_loaded(name: str) -> bool:
+    """Check whether an addon loaded successfully.
+
+    >>> import kindred_sdk as sdk
+    >>> sdk.is_addon_loaded("gears")
+    True
+    """
+    registry = _get_registry()
+    if registry is None:
+        return False
+    return registry.is_loaded(name)
+
+
+def addon_version(name: str):
+    """Return the version string for an addon, or None if not found.
+
+    >>> import kindred_sdk as sdk
+    >>> sdk.addon_version("gears")
+    '0.1.0'
+    """
+    registry = _get_registry()
+    if registry is None:
+        return None
+    manifest = registry.get(name)
+    if manifest is None:
+        return None
+    return manifest.version
+
+
+def loaded_addons() -> list[str]:
+    """Return the names of all successfully loaded addons, in load order.
+
+    >>> import kindred_sdk as sdk
+    >>> sdk.loaded_addons()
+    ['sdk', 'solver', 'gears', 'datums', 'silo']
+    """
+    registry = _get_registry()
+    if registry is None:
+        return []
+    return [m.name for m in registry.loaded()]