fix: remove byref delegate parameters incompatible with Mono/Xamarin (issue #458)

source/Handlebars.Test/Issues/Issue458Tests.cs

@@ -0,0 +1,41 @@
+using Xunit;
+
+namespace HandlebarsDotNet.Test
+{
+    public class Issue458Tests
+    {
+        [Fact]
+        public void Issue458_BasicCompileAndRender_NoByRefDelegate()
+        {
+            // Validates the scenario that fails on Mono when byref delegates are used
+            var h = Handlebars.Create();
+            var render = h.Compile("{{input}}");
+            var result = render(new { input = 42 });
+            Assert.Equal("42", result);
+        }
+
+        [Fact]
+        public void Issue458_BlockHelper_NoByRefDelegate()
+        {
+            // Block helpers also exercise TemplateDelegate compilation
+            var h = Handlebars.Create();
+            h.RegisterHelper("loud", (writer, options, context, arguments) =>
+            {
+                options.Template(writer, context);
+            });
+            var render = h.Compile("{{#loud}}hello{{/loud}}");
+            var result = render(new { });
+            Assert.Equal("hello", result);
+        }
+
+        [Fact]
+        public void Issue458_NestedTemplates_NoByRefDelegate()
+        {
+            // Nested template compilation exercises the expression tree lambda paths
+            var h = Handlebars.Create();
+            var render = h.Compile("{{#each items}}{{this}},{{/each}}");
+            var result = render(new { items = new[] { "a", "b", "c" } });
+            Assert.Equal("a,b,c,", result);
+        }
+    }
+}