fix(health): evict deleted sites from the aggregator on the periodic site refresh

src/ZB.MOM.WW.ScadaBridge.Communication/Actors/CentralCommunicationActor.cs

@@ -499,7 +499,12 @@ public class CentralCommunicationActor : ReceiveActor
             var frozen = contacts.ToDictionary(
                 kvp => kvp.Key,
                 kvp => (IReadOnlyList<string>)kvp.Value.AsReadOnly());
-            return new SiteAddressCacheLoaded(frozen);
+
+            // Carry the full configured-site identifier set (not just the
+            // address-bearing subset in `frozen`) so the aggregator prunes only
+            // genuinely-deleted sites and never an addressless-but-configured one.
+            var knownSiteIds = sites.Select(s => s.SiteIdentifier).ToList();
+            return new SiteAddressCacheLoaded(frozen, knownSiteIds);
         }).PipeTo(self);
     }
 
@@ -570,6 +575,12 @@ public class CentralCommunicationActor : ReceiveActor
         }
 
         _log.Info("Site ClusterClient cache refreshed with {0} site(s)", _siteClients.Count);
+
+        // Self-healing eviction: a site deleted from configuration would otherwise
+        // linger in the aggregator as a permanently-offline tile (and live KPI
+        // sample source) forever. Prune on every refresh so it disappears within
+        // one refresh interval without needing a dedicated deletion event.
+        _serviceProvider.GetService<ICentralHealthAggregator>()?.PruneUnknownSites(msg.KnownSiteIds);
     }
 
     // TrackMessageForCleanup removed — the dicts it fed
@@ -650,7 +661,9 @@ public record RefreshSiteAddresses;
 /// discipline. The producer wraps the constructed buckets with
 /// <c>List&lt;T&gt;.AsReadOnly()</c> before piping to Self.
 /// </summary>
-internal record SiteAddressCacheLoaded(IReadOnlyDictionary<string, IReadOnlyList<string>> SiteContacts);
+internal record SiteAddressCacheLoaded(
+    IReadOnlyDictionary<string, IReadOnlyList<string>> SiteContacts,
+    IReadOnlyCollection<string> KnownSiteIds);
 
 /// <summary>
 /// Notification sent to debug view subscribers when the stream is terminated

src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/CentralHealthAggregator.cs

@@ -196,6 +196,20 @@ public class CentralHealthAggregator : BackgroundService, ICentralHealthAggregat
         return state;
     }
 
+    /// <inheritdoc />
+    public void PruneUnknownSites(IReadOnlyCollection<string> knownSiteIds)
+    {
+        var known = new HashSet<string>(knownSiteIds, StringComparer.Ordinal);
+        foreach (var siteId in _siteStates.Keys)
+        {
+            if (siteId == CentralHealthReportLoop.CentralSiteId || known.Contains(siteId))
+                continue;
+            if (_siteStates.TryRemove(siteId, out _))
+                _logger.LogInformation(
+                    "Site {SiteId} evicted from health aggregator (no longer configured)", siteId);
+        }
+    }
+
     /// <inheritdoc />
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {

src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ICentralHealthAggregator.cs

@@ -39,4 +39,16 @@ public interface ICentralHealthAggregator
     /// <param name="siteId">The string identifier of the site to look up.</param>
     /// <returns>The <see cref="SiteHealthState"/> for the site, or null if not yet seen.</returns>
     SiteHealthState? GetSiteState(string siteId);
+
+    /// <summary>
+    /// Removes tracked sites not in <paramref name="knownSiteIds"/> (i.e. deleted
+    /// from configuration). The synthetic central id is always retained.
+    /// Self-healing: called from the CentralCommunicationActor's periodic site
+    /// refresh, so a deleted site disappears within one refresh interval without
+    /// needing a dedicated deletion event. Without this the in-memory state only
+    /// ever grew, leaving a deleted site as a permanently-offline dashboard tile
+    /// (and a live KPI sample source) forever.
+    /// </summary>
+    /// <param name="knownSiteIds">The identifiers of all currently-configured sites.</param>
+    void PruneUnknownSites(IReadOnlyCollection<string> knownSiteIds);
 }