Fixed the warning about unsaved changes appearing only by chance (#1050)

app/MindWork AI Studio/Tools/MessageBusAnswer.cs

@@ -0,0 +1,22 @@
+namespace AIStudio.Tools;
+
+/// <summary>
+/// What one receiver says to a question on the message bus, cf. MessageBus.SendMessageUseFirstResult.
+/// </summary>
+/// <remarks>
+/// A bare result cannot tell an answer apart from "this is not my question". Most receivers are components
+/// which never narrow down their events, so every question reaches them, and the default they return looks
+/// like an answer: for a bool, it is false. Such a false used to drown out the chat, the only receiver which
+/// knows whether it has unsaved changes, and the warning about them appeared only by chance. That is why a
+/// receiver states that it answers, and every other one returns NONE.
+/// </remarks>
+/// <param name="IsAnswered">True, when the receiver handles the question.</param>
+/// <param name="Value">The answer. It means nothing unless IsAnswered is true.</param>
+/// <typeparam name="TResult">The type of the answer.</typeparam>
+public readonly record struct MessageBusAnswer<TResult>(bool IsAnswered, TResult? Value)
+{
+    /// <summary>
+    /// The receiver does not handle this question.
+    /// </summary>
+    public static readonly MessageBusAnswer<TResult> NONE = new(false, default);
+}