Add comprehensive tests for image processing nodes and refactor node imports

- Introduced new test files for image layer, image plane, normal scale, object normal rotation, shadeless, and temporary attributes.
- Implemented tests to validate the behavior of alpha curves, depth layers, and normal scales in various rendering engines.
- Refactored import paths for node groups to align with the new directory structure.
- Added checks for temporary attribute lifetimes and ensured proper cleanup without warnings.
- Enhanced CLI commands to require the Blender group and validate the presence of generated node assets before packaging.
- Updated packaging scripts to enforce the existence of necessary assets, preventing build failures.

nodes/common/material_slots.py

@@ -0,0 +1,25 @@
+"""Carry the input mesh's material slots onto generated geometry."""
+
+
+def inherit_material_slots(group, geometry, source):
+    nodes, links = group.nodes, group.links
+    size = nodes.new("GeometryNodeAttributeDomainSize")
+    size.component = "MESH"
+    links.new(source, size.inputs["Geometry"])
+    index = nodes.new("GeometryNodeInputIndex")
+    source_vertices = nodes.new("FunctionNodeCompare")
+    source_vertices.data_type, source_vertices.operation = "INT", "LESS_THAN"
+    links.new(index.outputs["Index"], source_vertices.inputs[2])
+    links.new(size.outputs["Point Count"], source_vertices.inputs[3])
+    join = nodes.new("GeometryNodeJoinGeometry")
+    # Multi-input links are prepended: source occupies the first point range.
+    links.new(geometry, join.inputs["Geometry"])
+    links.new(source, join.inputs["Geometry"])
+    material = nodes.new("GeometryNodeSetMaterialIndex")
+    material.inputs["Material Index"].default_value = 0
+    links.new(join.outputs["Geometry"], material.inputs["Geometry"])
+    delete = nodes.new("GeometryNodeDeleteGeometry")
+    delete.domain = "POINT"
+    links.new(material.outputs["Geometry"], delete.inputs["Geometry"])
+    links.new(source_vertices.outputs["Result"], delete.inputs["Selection"])
+    return delete.outputs["Geometry"]