Generate more logging

There should probably be more logging/comment generation in the generated code. The `Merger` doesn't generate any, and `XML` barely does either.

I'm not 100% sure what logs would provide the best "bang-for-buck" either...

Start by inspecting the generated code paths for Merger and XML, since the issue identifies those as having little or no logging or comment generation. Determine which generated operations would benefit most from observability, then define and confirm the scope before making changes. Done means the agreed logging or comments appear consistently in the generated output.

Written by the indexing model from the issue text.