feat(commons): batched WriteValues on the address-space sink

src/Core/ZB.MOM.WW.OtOpcUa.Commons/OpcUa/DeferredAddressSpaceSink.cs

@@ -26,6 +26,12 @@ public sealed class DeferredAddressSpaceSink : IOpcUaAddressSpaceSink, ISurgical
     public void WriteValue(string nodeId, object? value, uint statusCode, DateTime sourceTimestampUtc, AddressSpaceRealm realm)
         => _inner.WriteValue(nodeId, value, statusCode, sourceTimestampUtc, realm);
 
+    /// <inheritdoc />
+    // Forward the batch to the inner sink. Without this the interface's default per-item loop runs here and
+    // the one-lock-per-batch win is silently degraded back to one lock per value on every driver-role host
+    // (actors inject THIS wrapper, not the inner SdkAddressSpaceSink) — same trap as WireAlarmNotifiers above.
+    public void WriteValues(IReadOnlyList<ValueWrite> values) => _inner.WriteValues(values);
+
     /// <inheritdoc />
     public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime sourceTimestampUtc, AddressSpaceRealm realm)
         => _inner.WriteAlarmCondition(alarmNodeId, state, sourceTimestampUtc, realm);

src/Core/ZB.MOM.WW.OtOpcUa.Commons/OpcUa/IOpcUaAddressSpaceSink.cs

@@ -22,6 +22,21 @@ public interface IOpcUaAddressSpaceSink
     /// calls this once per NodeId (raw + every referencing UNS node) with the matching realm.</param>
     void WriteValue(string nodeId, object? value, uint statusCode, DateTime sourceTimestampUtc, AddressSpaceRealm realm);
 
+    /// <summary>Write a batch of Variable values. Semantically identical to calling
+    /// <see cref="WriteValue"/> per item; an SDK-backed sink overrides this to take its internal
+    /// lock ONCE per batch instead of once per value (the hot-path win). The default implementation
+    /// loops <see cref="WriteValue"/> so existing sinks and fakes behave unchanged.</summary>
+    /// <param name="values">The value writes to apply, in order.</param>
+    void WriteValues(IReadOnlyList<ValueWrite> values)
+    {
+        ArgumentNullException.ThrowIfNull(values);
+        for (var i = 0; i < values.Count; i++)
+        {
+            var v = values[i];
+            WriteValue(v.NodeId, v.Value, v.StatusCode, v.SourceTimestampUtc, v.Realm);
+        }
+    }
+
     /// <summary>Write an alarm-condition's full Part 9 state. When a real condition node has been
     /// materialised for <paramref name="alarmNodeId"/> via <see cref="MaterialiseAlarmCondition"/>,
     /// this projects the whole <see cref="AlarmConditionSnapshot"/>
@@ -165,6 +180,11 @@ public interface IOpcUaAddressSpaceSink
                       string referenceType = "Organizes");
 }
 
+/// <summary>One value write within a <see cref="IOpcUaAddressSpaceSink.WriteValues"/> batch.
+/// Same semantics per field as <see cref="IOpcUaAddressSpaceSink.WriteValue"/> (#519: status verbatim).</summary>
+public readonly record struct ValueWrite(
+    string NodeId, object? Value, uint StatusCode, DateTime SourceTimestampUtc, AddressSpaceRealm Realm);
+
 /// <summary>No-op sink. Bound by default so the actors are safe to run in dev / Mac /
 /// integration tests without a real SDK behind them.</summary>
 public sealed class NullOpcUaAddressSpaceSink : IOpcUaAddressSpaceSink