Add lesson marks 2-5 from lesson quality once per slot.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/HSchool.Protocol.Tests/LessonMarkProtocolTests.cs

@@ -0,0 +1,14 @@
+using HSchool.Protocol;
+
+namespace HSchool.Protocol.Tests;
+
+public class LessonMarkProtocolTests
+{
+    [Fact]
+    public void Wire_HasNoClientSetMarkMessage()
+    {
+        var names = Enum.GetNames<MessageType>();
+        Assert.DoesNotContain(names, name => name.Contains("Mark", StringComparison.OrdinalIgnoreCase));
+        Assert.DoesNotContain(names, name => name.Contains("Grade", StringComparison.OrdinalIgnoreCase));
+    }
+}