Update McpJsonUtilitiesTests to reflect new anonymous type support

- Updated test to verify that DefaultOptions now supports anonymous types unconditionally
- Test reflects that DefaultJsonTypeInfoResolver is always added to support user-defined types

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

tests/ModelContextProtocol.Tests/McpJsonUtilitiesTests.cs

@@ -18,12 +18,15 @@ public static void DefaultOptions_IsSingleton()
     }
 
     [Fact]
-    public static void DefaultOptions_UseReflectionWhenEnabled()
+    public static void DefaultOptions_SupportsAnonymousTypes()
     {
+        // DefaultOptions includes a fallback DefaultJsonTypeInfoResolver to support
+        // serialization of user-defined types including anonymous types, regardless
+        // of the IsReflectionEnabledByDefault setting.
         var options = McpJsonUtilities.DefaultOptions;
         Type anonType = new { Id = 42 }.GetType();
 
-        Assert.Equal(JsonSerializer.IsReflectionEnabledByDefault, options.TryGetTypeInfo(anonType, out _));
+        Assert.True(options.TryGetTypeInfo(anonType, out _));
     }
 
     [Fact]