Add new functionality for image rectification and depth metadata handling

- Implemented a preview tool for rectifying images with interactive aspect controls in `preview.py`.
- Added tests for depth metadata loading to ensure consistent schema usage in `test_depth_metadata.py`.
- Developed comprehensive tests for cutout calibration processes in `test_cutout_calibration.py`, including stability checks and depth calibration.
- Created tests for frame compositing operations in `test_frame_compositing.py`, ensuring correct handling of depth and transparency.
- Introduced material slot inheritance functionality in `material_slots.py` to manage geometry material assignments.
- Built shared shader nodes for material processing in `shader.py`, including roughness and bump mapping setups.

tests/support/nodes.py

@@ -9,14 +9,3 @@ CUTOUT_BUILDERS = {
     "DEPTH_SOLID": build_image_depth_cutout_group,
     "DEPTH_BALLOON": build_image_depth_balloon_group,
 }
-
-
-def validate_node_structure(node_group):
-    """Check visible sockets, default titles, and paired execution endpoints."""
-    nodes = [node for node in node_group.nodes if node.bl_idname not in {"NodeReroute", "NodeFrame"}]
-    assert all(not node.label for node in nodes), node_group.name
-    assert not any(node.bl_idname == "FunctionNodeInputString" for node in nodes), node_group.name
-    assert all(socket.is_linked or socket.hide for node in node_group.nodes for socket in node.outputs), node_group.name
-    for node in nodes:
-        if node.bl_idname in {"GeometryNodeRepeatInput", "GeometryNodeSimulationInput", "GeometryNodeForeachGeometryElementInput"}:
-            assert node.paired_output in node_group.nodes.values(), (node_group.name, node.name)