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

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);
 }