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/shader.py

@@ -0,0 +1,34 @@
+"""Build shared material inputs, roughness, and bump outputs."""
+BUMP_BASE_DISTANCE = 0.001
+
+
+def build_material_nodes(group):
+    nodes = group.nodes
+    group_input = nodes.new("NodeGroupInput")
+    group_output = nodes.new("NodeGroupOutput")
+    roughness_curve = nodes.new("ShaderNodeFloatCurve")
+    roughness_curve.mapping.initialize()
+    curve_points = roughness_curve.mapping.curves[0].points
+    curve_points[0].location = (0.0, 0.5)
+    curve_points[-1].location = (1.0, 0.1)
+    roughness_curve.mapping.update()
+    bump = nodes.new("ShaderNodeBump")
+    return group_input, group_output, roughness_curve, bump
+
+
+def connect_material_outputs(group, group_input, group_output, roughness_curve, bump, processed_alpha):
+    nodes, links = group.nodes, group.links
+    links.new(group_input.outputs["Color"], group_output.inputs["Color"])
+    links.new(group_input.outputs["Color"], roughness_curve.inputs["Value"])
+    links.new(
+        roughness_curve.outputs["Value"],
+        group_output.inputs["Roughness"],
+    )
+    links.new(processed_alpha, group_output.inputs["Alpha"])
+    links.new(group_input.outputs["Color"], bump.inputs["Height"])
+    bump_distance = nodes.new("ShaderNodeMath")
+    bump_distance.operation = "MULTIPLY"
+    bump_distance.inputs[1].default_value = BUMP_BASE_DISTANCE
+    links.new(group_input.outputs["Bump Scale"], bump_distance.inputs[0])
+    links.new(bump_distance.outputs[0], bump.inputs["Distance"])
+    links.new(bump.outputs["Normal"], group_output.inputs["Normal"])