fix(runtime): narrow ActorNodeWriteGateway catch + drop vacuous no-actor assertion

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/ActorNodeWriteGateway.cs

@@ -60,10 +60,20 @@ public sealed class ActorNodeWriteGateway : IOpcUaNodeWriteGateway
                 _logger.LogWarning("Operator write to {NodeId} rejected: {Reason}", nodeId, result.Reason);
             return new NodeWriteOutcome(result.Success, result.Reason);
         }
-        catch (Exception ex) // AskTimeoutException, actor faults, cancellation
+        catch (OperationCanceledException ex)
         {
-            _logger.LogWarning(ex, "Operator write to {NodeId} failed or timed out", nodeId);
+            _logger.LogWarning(ex, "Operator write to {NodeId} cancelled", nodeId);
+            return new NodeWriteOutcome(false, "write cancelled");
+        }
+        catch (AskTimeoutException ex)
+        {
+            _logger.LogWarning(ex, "Operator write to {NodeId} timed out", nodeId);
             return new NodeWriteOutcome(false, "write timeout");
         }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Operator write to {NodeId} failed unexpectedly", nodeId);
+            return new NodeWriteOutcome(false, "write error");
+        }
     }
 }

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Drivers/ActorNodeWriteGatewayTests.cs

@@ -75,15 +75,11 @@ public sealed class ActorNodeWriteGatewayTests : RuntimeActorTestBase
     [Fact]
     public async Task No_actor_registered_maps_to_writes_unavailable()
     {
-        var probe = CreateTestProbe();
         var gateway = new ActorNodeWriteGateway(resolveDriverHost: () => null, NullLogger.Instance);
 
         var outcome = await gateway.WriteAsync("eq-1/speed", 123.0, CancellationToken.None);
 
         outcome.Success.ShouldBeFalse();
         outcome.Reason.ShouldBe("writes unavailable");
-
-        // The resolver returned null, so nothing should have been messaged anywhere.
-        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(200));
     }
 }