Refactor image mesh processing and background removal functionality

- Updated NODE_GROUP_NAME from "O Refine DA3 Surface" to "O DA3 Surface".
- Introduced `remove_surface_background` function to filter out background faces and compact geometry.
- Enhanced `build_image_mesh` to conditionally remove background faces based on a new property.
- Added `snapform_remove_background` and `snapform_keep_original` properties to operators for better control over background handling.
- Updated UI to reflect new properties and improved resolution scaling logic.
- Refactored tests to cover new background removal functionality and ensure proper geometry handling.
- Adjusted geometry nodes and validation scripts to remove references to background handling.

tools/validate_geometry_nodes_asset.py

@@ -51,7 +51,7 @@ def main():
     group_inputs = [
         node for node in group.nodes if node.bl_idname == "NodeGroupInput"
     ]
-    assert len(group_inputs) >= 8
+    assert len(group_inputs) >= 7
     for node in group_inputs:
         visible_outputs = [
             output for output in node.outputs if output.name and not output.hide
@@ -75,7 +75,6 @@ def main():
     assert [item.name for item in panels["Culling"].interface_items] == [
         "Confidence",
         "Stretch",
-        "Background",
     ]
     assert [item.name for item in panels["Options"].interface_items] == [
         "Fix Topology",
@@ -116,7 +115,7 @@ def main():
     evaluated = obj.evaluated_get(bpy.context.evaluated_depsgraph_get())
     result = evaluated.to_mesh()
     try:
-        assert len(result.polygons) == 1
+        assert len(result.polygons) == 2
         assert "UVMap" in result.attributes
         assert result.attributes["UVMap"].data_type == "FLOAT2"
     finally: