Please add an output Image_a for the Compare Images node

In the loop workflow, Compare Images does not update the comparison image in each loop. Please add an Image_a output to the Compare Images node.

Start by locating the Compare Images node implementation and its outputs, then trace how it behaves in the loop workflow. Confirm the existing comparison image handling and determine where the Image_a output should be exposed. Done means Image_a is available from Compare Images and updates correctly on each loop iteration.

Written by the indexing model from the issue text.