fix(auditlog): prune per-site reconciliation state and pull-channel caches for sites absent from the enumeration; bound the abandoned-id set (review 2026-10-21 06/MEM-2)

src/ZB.MOM.WW.ScadaBridge.AuditLog/Central/GrpcPullSiteCallsClient.cs

@@ -214,6 +214,8 @@ public sealed class GrpcPullSiteCallsClient : IPullSiteCallsClient
         string siteId, CancellationToken ct)
     {
         var sites = await _sites.EnumerateAsync(ct).ConfigureAwait(false);
+        // Review 2026-10-21 06/MEM-2: drop channels for sites/addresses no longer enumerated.
+        (_invoker as IGrpcChannelCachePruner)?.RetainOnly(sites);
         foreach (var site in sites)
         {
             if (string.Equals(site.SiteId, siteId, StringComparison.Ordinal) &&
@@ -275,13 +277,13 @@ public sealed class GrpcPullSiteCallsClient : IPullSiteCallsClient
 /// issues the unary <c>PullSiteCallsAsync</c> call. The cache is keyed by
 /// endpoint string, so a changed site address (NodeA→NodeB failover flip / an
 /// edited gRPC address) is reached as soon as the resolver hands the new endpoint
-/// to <see cref="InvokeAsync"/>. The channel for a previous address lingers idle
-/// until <see cref="Dispose"/> (idle channels hold no streams — a minor cache
-/// footprint cost, not a correctness or liveness gap). Sibling of
+/// to <see cref="InvokeAsync"/>. The channel for a previous address (or a deleted
+/// site) is evicted and disposed by <see cref="RetainOnly"/>, which the client calls
+/// with every site enumeration (review 2026-10-21 06/MEM-2). Sibling of
 /// <see cref="GrpcPullAuditEventsInvoker"/>.
 /// </summary>
 public sealed class GrpcPullSiteCallsInvoker
-    : GrpcPullSiteCallsClient.IPullSiteCallsInvoker, IDisposable
+    : GrpcPullSiteCallsClient.IPullSiteCallsInvoker, IDisposable, IGrpcChannelCachePruner
 {
     private readonly ConcurrentDictionary<(string Site, string Endpoint), GrpcChannel> _channels = new();
     private readonly CommunicationOptions _options;
@@ -358,6 +360,10 @@ public sealed class GrpcPullSiteCallsInvoker
             },
         }.WithMessageLimits().WithSiteCredentials(_pskProvider, siteId));
 
+    /// <inheritdoc />
+    public void RetainOnly(IReadOnlyList<SiteEntry> liveSites) =>
+        GrpcChannelCachePruning.RetainOnly(_channels, liveSites);
+
     /// <summary>Disposes all cached channels.</summary>
     public void Dispose()
     {