feat: add IHasDynamicMultiviewLayout interface and MultiviewParticipantSource class for dynamic layout support

src/PepperDash.Essentials.Core/DeviceTypeInterfaces/IHasDynamicMultiviewLayout.cs

@@ -0,0 +1,60 @@
+using Newtonsoft.Json;
+using System.Collections.Generic;
+
+namespace PepperDash.Essentials.Core.DeviceTypeInterfaces;
+
+/// <summary>
+/// Defines a device (e.g. a multiview-capable video decoder) that can build a multiview tile
+/// layout at runtime from a set of sources with priority values, rather than only supporting
+/// pre-configured/named layouts. Implementing this interface (instead of requiring consumers to
+/// reference the hardware-specific plugin type directly) lets other plugins (e.g. a room plugin)
+/// drive dynamic, priority-based layouts on the device without taking a compile-time dependency on
+/// the specific hardware plugin that implements it.
+/// </summary>
+public interface IHasDynamicMultiviewLayout
+{
+    /// <summary>
+    /// Computes and applies a multiview layout from the given participant sources (ordered by
+    /// priority) and an optional active presentation source.
+    /// </summary>
+    /// <param name="participantSources">Sources to place in participant tiles, each with a priority (lower value = higher priority).</param>
+    /// <param name="presentationSourceKey">Device key for the active presentation source, or null/empty if no presentation is active.</param>
+    /// <returns>True if the layout was successfully applied.</returns>
+    bool ApplyDynamicLayout(IReadOnlyList<MultiviewParticipantSource> participantSources, string presentationSourceKey);
+}
+
+/// <summary>
+/// Represents a single source eligible for placement in a dynamic multiview layout, along with
+/// its priority. Lower priority values are placed first / given more prominent tiles (i.e. lower
+/// number = higher priority).
+/// </summary>
+public class MultiviewParticipantSource
+{
+    /// <summary>
+    /// The device key of the source to place in a tile.
+    /// </summary>
+    [JsonProperty("sourceKey")]
+    public string SourceKey { get; set; }
+
+    /// <summary>
+    /// The priority of this source. Lower values are placed first / given more prominent tiles.
+    /// </summary>
+    [JsonProperty("priority")]
+    public int Priority { get; set; }
+
+    /// <summary>
+    /// Parameterless constructor for deserialization.
+    /// </summary>
+    public MultiviewParticipantSource()
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the MultiviewParticipantSource class.
+    /// </summary>
+    public MultiviewParticipantSource(string sourceKey, int priority)
+    {
+        SourceKey = sourceKey;
+        Priority = priority;
+    }
+}