It appears that Steam has made a change so that all Free-to-Play games now show up in your library regardless of whether you have requested them. This really clutters up the library and makes it hard to find the games I actually do want to install. I know I can limit my library to just installed games, but I’d rather have it go back to the way it was, only showing games I have purchased. Is there any way to do that?
As of a few moments ago, the answer is “Restart and update Steam”. This was a bug, which Valve has fixed; the moment you restart Steam so it can update again, the games should be removed from your library if they never belonged there in the first place.