Add tools and tests for AnyImage model management and documentation

- Implement sync_models.py for preparing and uploading ONNX artifacts.
- Create build_node.py for building and validating Blender scripts.
- Add docs.py for building and previewing documentation with Mike or MkDocs.
- Introduce model_exports.py for exporting PyTorch models to ONNX format.
- Develop pack.py for packaging the project with dependencies for different platforms.
- Add test_sync_models.py to validate sync_models functionality.
- Add test_tool_commands.py to ensure repository tools have correct command scripts.
- Initialize tools package with __init__.py.

src/anyimage/common/node.py

@@ -0,0 +1,47 @@
+from pathlib import Path
+
+import bpy
+
+
+NODE_ASSET_NAME = "O_AnyImage.blend"
+
+
+def node_asset_path():
+    return Path(__file__).resolve().parents[1] / "assets" / NODE_ASSET_NAME
+
+
+def load_node_group(group_name):
+    existing = bpy.data.node_groups.get(group_name)
+    if existing is not None:
+        return existing
+
+    asset_path = node_asset_path()
+    if not asset_path.is_file():
+        raise RuntimeError(f"Missing node asset: {asset_path}")
+    if bpy.app.version < (5, 0, 0):
+        directory = str(asset_path) + "/NodeTree/"
+        result = bpy.ops.wm.append(
+            filepath=directory + group_name,
+            directory=directory,
+            filename=group_name,
+            link=False,
+            do_reuse_local_id=True,
+        )
+        if "FINISHED" not in result:
+            raise RuntimeError("Unable to append the node asset")
+        node_group = bpy.data.node_groups.get(group_name)
+        if node_group is None:
+            raise RuntimeError("Appended node asset is unavailable")
+        node_group.use_fake_user = True
+        return node_group
+
+    with bpy.data.libraries.load(str(asset_path), link=True) as (source, target):
+        if group_name not in source.node_groups:
+            raise RuntimeError(f"Node asset is missing {group_name}")
+        target.node_groups = [group_name]
+    linked_group = target.node_groups[0]
+    node_group = bpy.data.pack_linked_ids_hierarchy(root_id=linked_group)
+    if linked_group != node_group and linked_group.users == 0:
+        bpy.data.node_groups.remove(linked_group)
+    node_group.use_fake_user = True
+    return node_group