feat(notification-outbox): CommunicationService per-site KPI accessor

tests/ScadaLink.Communication.Tests/CommunicationServiceTests.cs

@@ -4,6 +4,7 @@ using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using ScadaLink.Commons.Messages.Deployment;
 using ScadaLink.Commons.Messages.Notification;
+using ScadaLink.Commons.Types.Notifications;
 
 namespace ScadaLink.Communication.Tests;
 
@@ -209,6 +210,32 @@ public class CommunicationServiceTests : TestKit
         Assert.Equal(3, result.QueueDepth);
     }
 
+    [Fact]
+    public async Task GetPerSiteNotificationKpisAsync_AsksOutboxProxyDirectly()
+    {
+        var service = new CommunicationService(
+            Options.Create(new CommunicationOptions()),
+            NullLogger<CommunicationService>.Instance);
+        var probe = CreateTestProbe();
+        service.SetNotificationOutbox(probe.Ref);
+
+        var request = new PerSiteNotificationKpiRequest("corr-ps");
+        var task = service.GetPerSiteNotificationKpisAsync(request);
+
+        var received = probe.ExpectMsg<PerSiteNotificationKpiRequest>();
+        Assert.Same(request, received);
+        var reply = new PerSiteNotificationKpiResponse(
+            "corr-ps", true, null,
+            new[] { new SiteNotificationKpiSnapshot("plant-a", 2, 0, 0, 5, null) });
+        probe.Reply(reply);
+
+        var result = await task;
+        Assert.Same(reply, result);
+        Assert.True(result.Success);
+        Assert.Single(result.Sites);
+        Assert.Equal("plant-a", result.Sites[0].SourceSiteId);
+    }
+
     /// <summary>
     /// Stand-in for CentralCommunicationActor: verifies the message is wrapped
     /// in a SiteEnvelope targeting the requested site and replies with a typed