feat: add IRoutingSinkWithLayouts interface to support layouts with multiple tile sinks

src/PepperDash.Essentials.Core/Routing/IRoutingSinkWithLayouts.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using PepperDash.Core;
+using PepperDash.Essentials.Core.Routing;
+
+namespace PepperDash.Essentials.Core;
+
+
+/// <summary>
+/// Defines a routing sink (endpoint) device that supports layouts with multiple tile sinks.
+/// Implements IRoutingSource so the windowed output of the layout can be routed to other devices.
+/// </summary>
+public interface IRoutingSinkWithLayouts : IRoutingSource
+{
+    /// <summary>
+    /// Gets the collection of window tile sinks for this routing sink with layouts.
+    /// Each tile sink represents a single window/tile in the layout and can be routed independently.
+    /// </summary>
+    Dictionary<int, IRoutingSinkWithFeedback> WindowTileSinks { get; }
+}