docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

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

@@ -14,6 +14,9 @@ public interface ISubscribable
     ///     The driver MAY fire <see cref="OnDataChange"/> immediately with the current value
     ///     (initial-data callback per OPC UA convention) and again on every change.
     /// </summary>
+    /// <param name="fullReferences">The full references of the attributes to subscribe to.</param>
+    /// <param name="publishingInterval">The desired interval at which to receive data change notifications.</param>
+    /// <param name="cancellationToken">A cancellation token to observe for cancellation.</param>
     /// <returns>An opaque subscription handle the caller passes to <see cref="UnsubscribeAsync"/>.</returns>
     Task<ISubscriptionHandle> SubscribeAsync(
         IReadOnlyList<string> fullReferences,
@@ -21,6 +24,9 @@ public interface ISubscribable
         CancellationToken cancellationToken);
 
     /// <summary>Cancel a subscription returned by <see cref="SubscribeAsync"/>.</summary>
+    /// <param name="handle">The subscription handle to cancel.</param>
+    /// <param name="cancellationToken">A cancellation token to observe for cancellation.</param>
+    /// <returns>A task representing the asynchronous unsubscribe operation.</returns>
     Task UnsubscribeAsync(ISubscriptionHandle handle, CancellationToken cancellationToken);
 
     /// <summary>