feat: Add new Geometry Nodes groups for image relief and shadeless shader

- Implemented the "O Image Relief Plane" Geometry Nodes group to create a fixed-base image relief using depth images and various parameters.
- Created the "O Shadeless" shader node group to display color without scene lighting while preserving shadows and reflections.
- Introduced a preview feature for node groups, allowing for interactive visualization of node arrangements in an HTML format.
- Added a template HTML file for rendering node previews with customizable views and controls.

tests/depth_surface_test_support.py

@@ -11,14 +11,13 @@ ROOT = Path(__file__).parents[1]
 
 sys.path.insert(0, str(ROOT / "src"))
 
-sys.path.insert(0, str(ROOT / "tools" / "node_assets"))
 
-from cutout import build_cutout_group
+from node_asset_test_support import CUTOUT_BUILDERS
 
 
 def surface(*, step=6.0, size=1.0, resolution=2, wrapper=False):
     bpy.ops.wm.read_factory_settings(use_empty=True)
-    group = build_cutout_group("DEPTH_SOLID")
+    group = CUTOUT_BUILDERS["DEPTH_SOLID"]()
     # Two columns with a complete depth jump along their common boundary.
     points = [
         (x * size / resolution, y * size / resolution, 0)