Various improvements, some of which actually fix a test

[maackle]

This is kind of a big PR to fix one test, but it took a while to figure out the problem, and all of the changes I believe are improvements:

• make AppStatusFx (previously AppStatusTransitionEffects) #[must_use]
  • this helps ensure that any time an app state transition occurs, a followup processing of the after-effects must be done at some point to reconcile cell state with app state
• make AppStatusFx a monoid
  • this just means that it's easy to fold over a collection of FX to get a single FX to process, which allows us to effectively process after-effects from multiple state transitions, which is especially powerful when combined with must_use
• reorders the registration of dnas, in particular the "extra dnas" that get added by SweetConductor

[neonphog]

lgtm