feat(sdk): addon asset path resolution — addon_resource() (#389)

Add kindred_sdk.addon_resource(name, relative_path) that resolves
bundled asset paths relative to an addon's root directory. Looks up
the addon manifest from AddonRegistry for the install root, joins
the relative path, and validates existence on disk.

Raises LookupError if the addon is not registered, FileNotFoundError
if the resolved path does not exist.

Closes #389

mods/sdk/kindred_sdk/__init__.py

@@ -24,7 +24,12 @@ 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.registry import (
+    addon_resource,
+    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
@@ -33,6 +38,7 @@ from kindred_sdk.version import SDK_VERSION
 __all__ = [
     "SDK_VERSION",
     "active_origin",
+    "addon_resource",
     "addon_version",
     "available_contexts",
     "context_history",

mods/sdk/kindred_sdk/registry.py

@@ -3,6 +3,8 @@
 # Thin wrappers around FreeCAD.KindredAddons (AddonRegistry) so addons
 # use a stable SDK import instead of reaching into FreeCAD internals.
 
+import os
+
 import FreeCAD
 
 
@@ -51,3 +53,47 @@ def loaded_addons() -> list[str]:
     if registry is None:
         return []
     return [m.name for m in registry.loaded()]
+
+
+def addon_resource(name: str, relative_path: str) -> str:
+    """Resolve a bundled asset path for an addon.
+
+    Parameters
+    ----------
+    name : str
+        Addon name as declared in its ``package.xml`` (e.g. ``"silo"``).
+    relative_path : str
+        Path relative to the addon's root directory
+        (e.g. ``"icons/silo_commit.svg"``).
+
+    Returns
+    -------
+    str
+        Absolute path to the resolved file.
+
+    Raises
+    ------
+    LookupError
+        If the addon is not registered.
+    FileNotFoundError
+        If the resolved path does not exist on disk.
+
+    >>> import kindred_sdk as sdk
+    >>> sdk.addon_resource("silo", "icons/silo_commit.svg")
+    '/home/.../mods/silo/freecad/icons/silo_commit.svg'
+    """
+    registry = _get_registry()
+    if registry is None:
+        raise LookupError(
+            f"Addon registry not initialized; cannot resolve resource for '{name}'"
+        )
+    manifest = registry.get(name)
+    if manifest is None:
+        raise LookupError(f"Addon '{name}' is not registered")
+
+    resolved = os.path.join(manifest.addon_root, relative_path)
+    if not os.path.exists(resolved):
+        raise FileNotFoundError(
+            f"Resource not found: {resolved} (addon '{name}', path '{relative_path}')"
+        )
+    return resolved