Fixed chats not loading in the v26.10.1 pre-release and added a trim smoke test (#1128)

app/TrimSmokeTest/JsonRoot.cs

@@ -0,0 +1,10 @@
+using System.Text.Json;
+
+namespace AIStudio.TrimSmokeTest;
+
+/// <summary>
+/// A type which AI Studio reads or writes as JSON on its own, together with the options it uses for that.
+/// </summary>
+/// <param name="Type">The type which gets serialized. Whatever it holds gets checked along with it.</param>
+/// <param name="Options">The options AI Studio passes to System.Text.Json for this type.</param>
+public sealed record JsonRoot(Type Type, JsonSerializerOptions Options);