Stream the answers again whenever tools are in play (#986)

app/MindWork AI Studio/Tools/ToolCallingSystem/Harness/ToolCallingStreamEvent.cs

@@ -0,0 +1,36 @@
+using AIStudio.Provider;
+
+namespace AIStudio.Tools.ToolCallingSystem.Harness;
+
+/// <summary>
+/// One event of a streamed round of a tool calling conversation.
+/// </summary>
+/// <remarks>
+/// Text arrives while the round is still running, its outcome only at the end. A round which ends
+/// without a ROUND_COMPLETED event has failed: that is how a failed request or a truncated stream
+/// is told apart from a round which simply had nothing to say. The adapter has already told the
+/// user what went wrong in that case, so the loop ends without a message of its own.
+/// </remarks>
+/// <param name="Kind">What this event carries.</param>
+/// <param name="Delta">The piece of text, set for TEXT_DELTA events only.</param>
+/// <param name="Round">The round's outcome, set for ROUND_COMPLETED events only.</param>
+public sealed record ToolCallingStreamEvent(ToolCallingStreamEventKind Kind, ContentStreamChunk? Delta, ToolCallingRound? Round)
+{
+    /// <summary>
+    /// Creates an event for a piece of text, along with the sources it brought.
+    /// </summary>
+    /// <param name="delta">The chunk to show.</param>
+    public static ToolCallingStreamEvent TextDelta(ContentStreamChunk delta) => new(ToolCallingStreamEventKind.TEXT_DELTA, delta, null);
+    
+    /// <summary>
+    /// Creates an event for a piece of text without any sources.
+    /// </summary>
+    /// <param name="text">The text to show.</param>
+    public static ToolCallingStreamEvent TextDelta(string text) => new(ToolCallingStreamEventKind.TEXT_DELTA, new ContentStreamChunk(text, []), null);
+    
+    /// <summary>
+    /// Creates the event which ends a round.
+    /// </summary>
+    /// <param name="round">The round's outcome.</param>
+    public static ToolCallingStreamEvent RoundCompleted(ToolCallingRound round) => new(ToolCallingStreamEventKind.ROUND_COMPLETED, null, round);
+}