Added the Model Comparison assistant for blind comparisons of two models (#1009)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Chat/Embedded/IEmbeddedChatStore.cs

@@ -0,0 +1,28 @@
+namespace AIStudio.Chat.Embedded;
+
+/// <summary>
+/// Where the embedded chats of an assistant live, e.g., in a folder of the assistant below the data directory.
+/// </summary>
+/// <remarks>
+/// An embedded chat never lives in a workspace: it belongs to the assistant which shows it, and the assistant decides
+/// how long it stays. The store finds a chat by its ID, ChatThread.ChatId.
+/// </remarks>
+public interface IEmbeddedChatStore
+{
+    /// <summary>
+    /// Loads a chat.
+    /// </summary>
+    /// <param name="chatId">The ID of the chat.</param>
+    /// <param name="token">The cancellation token.</param>
+    /// <returns>The chat, or null when it has no stored thread yet.</returns>
+    /// <exception cref="InvalidDataException">This version cannot open the stored chat; the file stays as it is.</exception>
+    public Task<ChatThread?> LoadThreadAsync(Guid chatId, CancellationToken token = default);
+
+    /// <summary>
+    /// Stores a chat, in place of what was stored of it before.
+    /// </summary>
+    /// <param name="thread">The chat, with its ID.</param>
+    /// <param name="token">The cancellation token.</param>
+    /// <exception cref="FileNotFoundException">What the chat belonged to was deleted meanwhile; nothing is left to store.</exception>
+    public Task SaveThreadAsync(ChatThread thread, CancellationToken token = default);
+}