Generated the JSON contracts of visual briefings and model answers at compile time (#1151)

app/Tests/Serialization/JsonDefaultsTests.cs

@@ -8,7 +8,7 @@ namespace AIStudio.Tests.Serialization;
 /// </summary>
 /// <remarks>
 /// Files written by an older version of AI Studio lack every property added since, and an answer of a
-/// provider, of the runtime, or of a service leaves out whatever it has nothing to say about. Reading them has
+/// provider, of the runtime, of a service, or of a model leaves out whatever it has nothing to say about. Reading them has
 /// to give those properties their defaults, as a new object has them, e.g., a sub-object of the settings
 /// instead of null. Source generation in .NET 10 breaks this for init-only properties: it sets them all while
 /// creating the object, and a property missing in the JSON gets the default of its type instead
@@ -25,6 +25,9 @@ public sealed class JsonDefaultsTests
     [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.ProviderAnswers))]
     [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.RuntimeAnswers))]
     [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.ServiceAnswers))]
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.VisualBriefingStored))]
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.VisualBriefingAnswers))]
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.ModelAnswers))]
     public void AnEmptyObjectGetsTheDefaultsOfANewOne(JsonTestRoot root)
     {
         var baseline = JsonReflectionBaseline.Of(root.Options);