message: Explain why not busy is ignored
diff: @@ -186,6 +186,12 @@ export default createReactClass({
  stageErrorText: null,
  });
  }
  + // The JS SDK eagerly reports itself as "not busy" right after any
  + // immediate work has completed, but that's not really what we want at
  + // the UI layer, so we ignore this signal and show a spinner until
  + // there's a new screen to show the user. This is implemented by setting
  + // `busy: false` in `_authStateUpdated`.
  + // See also https://github.com/vector-im/riot-web/issues/12546
  },
  _setFocus: function() {
  