Thanks for the pointers everyone!
I ended up putting together a thing that uses OpenAI's API with gpt-4o-mini to suggest OSM tags for a picture: https://github.com/iandees/image-to-osm
I'll try putting it up on the web somewhere if there's interest. I spent about 15ยข testing it a few dozen times:
@ian Wow! I just thought, adding a button to Every Door to use this would be sooo easy. But the multitude of edge cases makes me wary.