Rename the frontend comm to something more specific

[lionel-]

Part of #265

While porting the frontend comm to use generated types we noticed we were getting confusingly named json files like the "Frontend frontend" and the "Frontend backend". To avoid this it would be nice to come up with a more specific name.

@jmcphers suggested the "UI comm". This also could be the "user comm" or the "client comm".

[seeM]

My vote is for "UI comm" as well. "user comm" and "client comm" feel a tad more generic, and might run into similar issues to "frontend comm" (e.g. you might have "client comm clients" or "users of the user comm")