Add tests for image layer, image plane, inventory, saved layout, commands, documentation, manifest, and packaging

- Implement tests for image layer functionality including alpha curve and depth layer behavior.
- Create tests for image plane evaluation and modifier input handling.
- Add tests to verify the saved asset inventory and its persistence.
- Introduce tests for the documentation command to ensure correct project version deployment.
- Validate the extension manifest structure and required permissions.
- Develop tests for the packaging process, ensuring correct platform handling and dependency management.
- Enhance image depth plane group functionality with new split threshold input and surface processing.

tests/support/materials.py

@@ -0,0 +1,17 @@
+import bpy
+import pytest
+from tests.support.paths import PROJECT_ROOT
+from tools.nodes.groups.image_layer import build_image_layer_group
+
+
+@pytest.fixture
+def image_layer(request):
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    if getattr(request, "param", "definition") == "asset":
+        with bpy.data.libraries.load(str(PROJECT_ROOT / "src/anyimage/assets/O_AnyImage.blend")) as (_, target):
+            target.node_groups = ["O Image Layer"]
+        group = target.node_groups[0]
+    else:
+        group = build_image_layer_group()
+    yield group
+    bpy.ops.wm.read_factory_settings(use_empty=True)