TODO list

Figure out how to build for arm64 & x86_64, which means.. figuring that out for libguile and spotiqueue_worker, too. :(
Ensure that focus is always something sensible (read: search bar) on app startup. With and without displaying login flow. Might be complex: http://www.extelligentcocoa.org/the-strange-case-of-initialfirstresponder/
We really need proper auth-failure handling. Especially an invalid refresh token just makes the app crash 👎
Add all features to app menus for discoverability.
When moving tracks in queue consider scrolling such that there's a 3-4 track "buffer" of not-selected tracks between the selected block and the edge of the view.
Get Xcode to build my dependencies from source so we can once and for all squash the warnings about MACOS_DEPLOYMENT_TARGET, etc., as well as the unmitigated disaster which is the libraries-from-Homebrew hassle.
Little Credits or Help screen
Idea: backspace in search window takes you "up" a detail level if you've done a detail browse. AKA "show previous search results". One approach could be to store the list of tracks returned by various searches, up to e.g. 10 ago.

Things i can't do much about

Leave the app idle for a long time, play a track -> spotiqueue_worker session is invalid and client shuts down. librespot-org/librespot#276, librespot-org/librespot#609 Is this fixed in librespot-org/librespot#783?
Automatically switch audio output sink when using Sound.prefpane. RustAudio/rodio#327
very quick fade in / out when pausing? - maybe shorten the audio buffer in librespot? Turns out it's something i can't easily fix, because they also adjust audio volume per buffer chunk, grr.

Allow filtering search results through a hook. E.g., never show Coldplay in the results.
Last.fm scrobbling with Guile.
Get search results as a list.
Can i remove a layer of boilerplate by using the @_cdecl("foo") directly in Swift? Yes, you can.