The feed doesn't flash "Empty" while the persona is switched to

LoadSession said the session was loaded before SwitchPersona had set the persona, so a render in between (any
CascadingState change) showed the feed a loaded session without a persona, and it said "Empty" until the persona came.
The session counts as loaded once the persona is known, or couldn't be used. StreamingTests took that flash for the
feed and, on a slower start, posted before the stream was open; it now waits until the app has subscribed to the home
stream.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

LayerComponents/CascadingState.razor

@@ -113,8 +113,11 @@
 			return;
 		}
 
-		IsSessionLoaded = true;
+		// loaded once the persona is known (or couldn't be used): a page rendered while it is switched to would otherwise
+		// see a loaded session without one, and the feed would say it is empty
 		await SwitchPersona(personaId, cancellationToken);
+		IsSessionLoaded = true;
+		StateHasChanged();
 	}
 
 	/// <summary>Acts as another of the root's personas; every page showing persona data reloads.</summary>