feat(deploy): RefreshDeploymentAsync send method

Add CommunicationService.RefreshDeploymentAsync — the typed send method
for the small notify-and-fetch wire message (RefreshDeploymentCommand).
Mirrors DeployInstanceAsync exactly: SiteEnvelope + Ask<DeploymentStatusResponse>
bounded by DeploymentTimeout. CentralCommunicationActor needs no change
(HandleSiteEnvelope is fully generic — all SiteEnvelope messages forward
to /user/site-communication without a per-type switch). Adds a parallel
routing test asserting the envelope reaches the site ClusterClient.

src/ZB.MOM.WW.ScadaBridge.Communication/CommunicationService.cs

@@ -134,6 +134,27 @@ public class CommunicationService
             envelope, _options.DeploymentTimeout, cancellationToken);
     }
 
+    /// <summary>
+    /// Sends a small "refresh deployment" notify to a site (notify-and-fetch).
+    /// Replaces <see cref="DeployInstanceAsync"/> on the wire: the site fetches the
+    /// config over HTTP rather than receiving it inline. Reply is the existing
+    /// DeploymentStatusResponse, bounded by the deployment timeout.
+    /// </summary>
+    /// <param name="siteId">The target site identifier.</param>
+    /// <param name="command">The refresh-deployment notify.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The deployment status response.</returns>
+    public async Task<DeploymentStatusResponse> RefreshDeploymentAsync(
+        string siteId, RefreshDeploymentCommand command, CancellationToken cancellationToken = default)
+    {
+        _logger.LogInformation(
+            "Sending RefreshDeploymentCommand to site {SiteId}, instance={Instance}, deploymentId={DeploymentId}",
+            siteId, command.InstanceUniqueName, command.DeploymentId);
+        var envelope = new SiteEnvelope(siteId, command);
+        return await GetActor().Ask<DeploymentStatusResponse>(
+            envelope, _options.DeploymentTimeout, cancellationToken);
+    }
+
     /// <summary>
     /// DeploymentManager-006: queries a site for the currently-applied deployment
     /// identity of a single instance. Used by the Deployment Manager before a

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/CentralCommunicationActorTests.cs

@@ -101,6 +101,25 @@ public class CentralCommunicationActorTests : TestKit
         Assert.Equal("dep1", ((DeployInstanceCommand)msg.Message).DeploymentId);
     }
 
+    [Fact]
+    public void ClusterClientRouting_RefreshDeploymentCommand_RoutesToSite()
+    {
+        var site = CreateSite("site1", "akka.tcp://scadabridge@host:8082");
+        var (actor, _, siteProbes) = CreateActorWithMockRepo(new[] { site });
+
+        Thread.Sleep(1000);
+
+        var command = new RefreshDeploymentCommand(
+            "dep1", "inst1", "rev1", "admin", DateTimeOffset.UtcNow,
+            "https://central:9000", "tok1");
+        actor.Tell(new SiteEnvelope("site1", command));
+
+        var msg = siteProbes["site1"].ExpectMsg<ClusterClient.Send>();
+        Assert.Equal("/user/site-communication", msg.Path);
+        Assert.IsType<RefreshDeploymentCommand>(msg.Message);
+        Assert.Equal("dep1", ((RefreshDeploymentCommand)msg.Message).DeploymentId);
+    }
+
     [Fact]
     public void UnconfiguredSite_MessageIsDropped()
     {