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

app/MindWork AI Studio/Provider/ProviderJsonOptions.cs

@@ -0,0 +1,38 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using AIStudio.Provider.Anthropic;
+using AIStudio.Provider.OpenAI;
+
+namespace AIStudio.Provider;
+
+/// <summary>
+/// The JSON options every provider request and response is read and written with.
+/// </summary>
+/// <remarks>
+/// They sit outside the provider base class so that the types which interpret a stream can share
+/// them without being a provider themselves. Those types are the ones worth testing, and a
+/// provider cannot be constructed in a test at all -- it reaches for the service provider in its
+/// constructor. Options rebuilt inside a test would be a second set of rules drifting away from
+/// the one that actually reads the wire.
+/// </remarks>
+public static class ProviderJsonOptions
+{
+    /// <summary>
+    /// The shared options.
+    /// </summary>
+    public static readonly JsonSerializerOptions OPTIONS = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+        Converters =
+        {
+            new JsonStringEnumConverter(JsonNamingPolicy.SnakeCaseLower),
+            new AnnotationConverter(),
+            new MessageBaseConverter(),
+            new SubContentConverter(),
+            new SubContentImageSourceConverter(),
+            new SubContentImageUrlConverter(),
+        },
+        AllowTrailingCommas = false
+    };
+}