What is the idiomatic way to use a ModelContext in a document based SwiftData app from a background thread? The relevant DocumentGroup initializers do not give us direct access to a ModelContainer, only to a ModelContext. Is it safe to take its modelContext.container and pass it around (for creating a ModelContext on it on a background thread) or to construct a ModelActor with it? Is it safe to e.g. put a ModelActor so created into the environment of the root view of the window and execute various async data operations on it in Tasks throughout the app, as long as these are dispatched from within the window whose root view's ModelContext was used for getting the ModelContainer?

I have multiple document based SwiftUI apps without any NavigationBar customization. Since upgrading to iOS 26 , when these apps launch, sometimes their navigation bar icons appear grey (as if only the button shadows were showing) and the document title is white, so it’s invisible. One of the apps has an Inspector: here, whenever the Inspector appears, the colors are correct. This behavior has been consistent since the first iOS 26 developer beta and can be reproduced on iOS 26.1 beta 23B5064e. So far I have only managed to reproduce this in light mode.