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

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

@@ -0,0 +1,14 @@
+namespace AIStudio.Provider.OpenAI;
+
+/// <summary>
+/// One line of a streamed Chat Completions answer, as the tool calling rounds read it.
+/// </summary>
+/// <remarks>
+/// The plain text path reads the very same lines through its own provider-specific type, which
+/// knows about text and about the sources some providers put in it. Reading a line twice costs
+/// nothing next to the request it arrived on, and it keeps the tool calls out of a type every
+/// provider implements -- including those which never call a tool.
+/// </remarks>
+/// <param name="Id">The ID of the answer.</param>
+/// <param name="Choices">The choices this line adds to.</param>
+public sealed record ChatCompletionToolStreamLine(string? Id, IList<ChatCompletionToolStreamChoice?>? Choices);