fix(health): acked SendAsync transport — report-loss counter restore is live, not dead code

src/ZB.MOM.WW.ScadaBridge.Host/AkkaHealthReportTransport.cs

@@ -6,13 +6,17 @@ using ZB.MOM.WW.ScadaBridge.Host.Actors;
 namespace ZB.MOM.WW.ScadaBridge.Host;
 
 /// <summary>
-/// Sends SiteHealthReport to the local SiteCommunicationActor via Akka ActorSelection.
-/// The SiteCommunicationActor forwards it to central.
+/// Sends SiteHealthReport to the local SiteCommunicationActor via Akka ActorSelection,
+/// which forwards it to central. The send is an acked round-trip (review 01 [Medium]):
+/// it Asks and awaits the central <see cref="SiteHealthReportAck"/>, so a lost or
+/// rejected report faults the sender's task (driving its counter-restore path).
 /// </summary>
 public class AkkaHealthReportTransport : IHealthReportTransport
 {
     private readonly AkkaHostedService _akkaService;
 
+    private static readonly TimeSpan AckTimeout = TimeSpan.FromSeconds(10);
+
     /// <summary>
     /// Initializes a new <see cref="AkkaHealthReportTransport"/> backed by the given Akka hosted service.
     /// </summary>
@@ -23,12 +27,15 @@ public class AkkaHealthReportTransport : IHealthReportTransport
     }
 
     /// <inheritdoc />
-    public void Send(SiteHealthReport report)
+    public async Task SendAsync(SiteHealthReport report, CancellationToken cancellationToken)
     {
-        var actorSystem = _akkaService.ActorSystem;
-        if (actorSystem == null) return;
+        var actorSystem = _akkaService.ActorSystem
+            ?? throw new InvalidOperationException("Actor system not started — health report not sent");
 
         var siteComm = actorSystem.ActorSelection("/user/site-communication");
-        siteComm.Tell(report, ActorRefs.NoSender);
+        var ack = await siteComm.Ask<SiteHealthReportAck>(report, AckTimeout, cancellationToken)
+            .ConfigureAwait(false);
+        if (!ack.Accepted)
+            throw new InvalidOperationException($"Health report #{report.SequenceNumber} rejected: {ack.Error}");
     }
 }