Artist disambiguation in paths

It would be nice to have artist disambiguation like album disambiguation in paths. It doesn't happen that often (for me), but in the rare case that I have music files from artists that happen to have the same artistname, I'd like to see the difference between them in my paths.

Start by locating the code that builds paths and the existing album-disambiguation handling, then trace how artist metadata is available when paths are generated. Clarify the desired path format and how same-named artists should be distinguished before changing behavior; done means artist disambiguation appears consistently without altering paths for unambiguous artists.

Written by the indexing model from the issue text.