Tidy the shell index wording and the tray test's usings

Author: chrisuthe

docs/ARCHITECTURE.md

@@ -582,7 +582,7 @@ the host's and the shell cannot follow a path into it.
 
 ## UI shell
 
-**What shipped, by paragraph.** The measurements below are long; these are the six "As shipped"
+**What shipped, by paragraph.** The measurements below are long; these are the "As shipped"
 paragraphs that say what the player does with them, so a reader after the shell rather than the
 numbers can go straight there:
 

src/Sendspin.Ui.Tests/TrayMenuTests.cs

@@ -2,6 +2,7 @@
 using Avalonia.Threading;
 using Microsoft.Extensions.Logging.Abstractions;
 using Sendspin.Player;
+using Sendspin.Player.ViewModels;
 using Xunit;
 
 namespace Sendspin.Ui.Tests;
@@ -107,7 +108,7 @@ private Tray(TrayIconController controller, ShellGraph graph)
 
         public TrayIconController Controller { get; }
 
-        public Sendspin.Player.ViewModels.MainViewModel ViewModel { get; }
+        public MainViewModel ViewModel { get; }
 
         public static Tray Attach()
         {