Python: .NET: Executor source gen for workflow executor routing (#3131)

* Roslyn Source Generators for Workflow Executor Routing.

* Update dotnet/src/Microsoft.Agents.AI.Workflows.Generators/ExecutorRouteGenerator.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* WIP.

* All fixed up except dangling sends/yields attriutes, working on that next.

* Add protocol-only generation for SendsMessage/YieldsOutput attributes

* Ensuring collections that can change order are sorted to enable pipeline caching.

* Improvents per PR feedback.

---------

Co-authored-by: alliscode <bentho@microsoft.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Models/ClassProtocolInfo.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Microsoft.Agents.AI.Workflows.Generators.Models;
+
+/// <summary>
+/// Represents protocol type information extracted from class-level [SendsMessage] or [YieldsOutput] attributes.
+/// Used by the incremental generator pipeline to capture classes that declare protocol types
+/// but may not have [MessageHandler] methods (e.g., when ConfigureRoutes is manually implemented).
+/// </summary>
+/// <param name="ClassKey">Unique identifier for the class (fully qualified name).</param>
+/// <param name="Namespace">The namespace of the class.</param>
+/// <param name="ClassName">The name of the class.</param>
+/// <param name="GenericParameters">The generic type parameters (e.g., "&lt;T&gt;"), or null if not generic.</param>
+/// <param name="IsNested">Whether the class is nested inside another class.</param>
+/// <param name="ContainingTypeChain">The chain of containing types for nested classes. Empty if not nested.</param>
+/// <param name="IsPartialClass">Whether the class is declared as partial.</param>
+/// <param name="DerivesFromExecutor">Whether the class derives from Executor.</param>
+/// <param name="HasManualConfigureRoutes">Whether the class has a manually defined ConfigureRoutes method.</param>
+/// <param name="ClassLocation">Location info for diagnostics.</param>
+/// <param name="TypeName">The fully qualified type name from the attribute.</param>
+/// <param name="AttributeKind">Whether this is from a SendsMessage or YieldsOutput attribute.</param>
+internal sealed record ClassProtocolInfo(
+    string ClassKey,
+    string? Namespace,
+    string ClassName,
+    string? GenericParameters,
+    bool IsNested,
+    string ContainingTypeChain,
+    bool IsPartialClass,
+    bool DerivesFromExecutor,
+    bool HasManualConfigureRoutes,
+    DiagnosticLocationInfo? ClassLocation,
+    string TypeName,
+    ProtocolAttributeKind AttributeKind)
+{
+    /// <summary>
+    /// Gets an empty result for invalid targets.
+    /// </summary>
+    public static ClassProtocolInfo Empty { get; } = new(
+        string.Empty, null, string.Empty, null, false, string.Empty,
+        false, false, false, null, string.Empty, ProtocolAttributeKind.Send);
+}