feat(core): add IBatchSubscribable batch data-change contract

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/ISubscribable.cs

@@ -51,3 +51,29 @@ public sealed record DataChangeEventArgs(
     ISubscriptionHandle SubscriptionHandle,
     string FullReference,
     DataValueSnapshot Snapshot);
+
+/// <summary>One changed attribute within a <see cref="DataChangeBatchEventArgs"/>.</summary>
+/// <param name="FullReference">Driver-side full reference of the changed attribute.</param>
+/// <param name="Snapshot">New value + quality + timestamps.</param>
+public sealed record DataChangeItem(string FullReference, DataValueSnapshot Snapshot);
+
+/// <summary>Event payload for <see cref="IBatchSubscribable.OnDataChangeBatch"/> — every attribute
+/// that changed within ONE production burst (a poll cycle, an inbound message, a stream chunk).</summary>
+/// <param name="SubscriptionHandle">The handle returned by the original <see cref="ISubscribable.SubscribeAsync"/> call.</param>
+/// <param name="Items">The changed attributes, one entry per changed tag. Never empty.</param>
+public sealed record DataChangeBatchEventArgs(
+    ISubscriptionHandle SubscriptionHandle,
+    IReadOnlyList<DataChangeItem> Items);
+
+/// <summary>
+///     Optional driver capability: data changes delivered one event per production burst instead of
+///     one event per tag. A driver implementing this raises <see cref="OnDataChangeBatch"/> once per
+///     burst AND continues raising the per-tag <see cref="ISubscribable.OnDataChange"/> for each item
+///     (legacy consumers: Galaxy cold reads, driver CLIs). A consumer subscribes to EXACTLY ONE of the
+///     two events — subscribing both double-delivers. DriverInstanceActor prefers the batch event.
+/// </summary>
+public interface IBatchSubscribable : ISubscribable
+{
+    /// <summary>Batched data-change notification — one raise per production burst.</summary>
+    event EventHandler<DataChangeBatchEventArgs>? OnDataChangeBatch;
+}