What installSceneAudio needs from the app.
The app's sound engine (only the scene-binding surface).
The loaded scene's root (LuxarScene), if it is in the scene.
LuxarScene
The when of the waypoint the opening story snapped to, if any.
when
Re-push the Layers panel's per-layer sound mutes onto the new nodes.
What installSceneAudio needs from the app.