Add unit tests for service functionality and model caching

- Implement tests for ben2 and da3 model caching to ensure models are reused for matching runtime keys.
- Verify service state management, including client registration, job cancellation, and client expiration.
- Test discovery file creation and removal based on service ownership.
- Ensure frame extraction functionality works without models and produces expected results.

tools/validate_depth_plane_asset.py

@@ -214,6 +214,13 @@ def main():
     ]
     assert len(surface_group_nodes) == 1
     assert surface_group_nodes[0].name == "O DA3 Surface Layer"
+    surface_inputs = [
+        item.name
+        for item in surface_group.interface.items_tree
+        if item.item_type == "SOCKET"
+        and item.in_out == "INPUT"
+    ]
+    assert surface_inputs == ["Color", "Alpha", "Bump Scale"]
     surface_outputs = [
         item.name
         for item in surface_group.interface.items_tree
@@ -232,14 +239,6 @@ def main():
         and item.name == "Background"
         for item in refine_group.interface.items_tree
     )
-    surface_depth_input = next(
-        item
-        for item in surface_group.interface.items_tree
-        if item.item_type == "SOCKET"
-        and item.in_out == "INPUT"
-        and item.name == "Depth"
-    )
-    assert surface_depth_input.socket_type == "NodeSocketFloat"
     assert not any(
         node.bl_idname in forbidden_outer_nodes
         for node in surface_material.node_tree.nodes