Stream the tool calling rounds of the Responses API

app/MindWork AI Studio/Provider/OpenAI/ResponsesStreamPart.cs

@@ -0,0 +1,19 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// What one line of a streamed Responses API call has to show to the user.
+/// </summary>
+/// <param name="TextDelta">The text this line carried, empty when it carried none.</param>
+/// <param name="Sources">The sources this line announced, empty when it announced none.</param>
+public readonly record struct ResponsesStreamPart(string TextDelta, IList<ISource> Sources)
+{
+    /// <summary>
+    /// The part of a line which says nothing to the user, such as a bookkeeping event.
+    /// </summary>
+    public static ResponsesStreamPart Nothing => new(string.Empty, []);
+    
+    /// <summary>
+    /// Whether this part has anything to show at all.
+    /// </summary>
+    public bool HasContent => this.TextDelta.Length > 0 || this.Sources.Count > 0;
+}