.NET: Fix broken workflow samples (#4800)

* Fix source generator bug that silently drops base class handler registrations for protocol-only partial executors

* Fixed xml comments and variable naming.

* Fix workflow samples broken due to routing change

dotnet/samples/03-workflows/Concurrent/Concurrent/Program.cs

@@ -72,6 +72,8 @@ public static class Program
 /// <summary>
 /// Executor that starts the concurrent processing by sending messages to the agents.
 /// </summary>
+[SendsMessage(typeof(ChatMessage))]
+[SendsMessage(typeof(TurnToken))]
 internal sealed partial class ConcurrentStartExecutor() :
     Executor("ConcurrentStartExecutor")
 {
@@ -97,7 +99,8 @@ internal sealed partial class ConcurrentStartExecutor() :
 /// <summary>
 /// Executor that aggregates the results from the concurrent agents.
 /// </summary>
-internal sealed class ConcurrentAggregationExecutor() :
+[YieldsOutput(typeof(string))]
+internal sealed partial class ConcurrentAggregationExecutor() :
     Executor<List<ChatMessage>>("ConcurrentAggregationExecutor")
 {
     private readonly List<ChatMessage> _messages = [];