feat(audit): M5.2 per-node stuck-count KPIs (T6) — repo per-node aggregation, actor message pair, CentralUI tiles

src/ZB.MOM.WW.ScadaBridge.SiteCallAudit/SiteCallAuditActor.cs

@@ -239,6 +239,7 @@ public class SiteCallAuditActor : ReceiveActor
         Receive<SiteCallDetailRequest>(HandleDetail);
         Receive<SiteCallKpiRequest>(HandleKpi);
         Receive<PerSiteSiteCallKpiRequest>(HandlePerSiteKpi);
+        Receive<PerNodeSiteCallKpiRequest>(HandlePerNodeKpi);
 
         // Task 5 (#22): central→site Retry/Discard relay for parked cached calls.
         Receive<RegisterCentralCommunication>(msg =>
@@ -817,6 +818,47 @@ public class SiteCallAuditActor : ReceiveActor
         }
     }
 
+    /// <summary>
+    /// Handles a per-node KPI request, using the same stuck cutoff and
+    /// interval bound as <see cref="HandleKpi"/>. Additive alongside
+    /// <see cref="HandlePerSiteKpi"/> — does not change per-site behaviour.
+    /// </summary>
+    private void HandlePerNodeKpi(PerNodeSiteCallKpiRequest request)
+    {
+        var sender = Sender;
+        var now = DateTime.UtcNow;
+        var stuckCutoff = now - _options.StuckAgeThreshold;
+        var intervalSince = now - _options.KpiInterval;
+
+        PerNodeKpiAsync(request.CorrelationId, stuckCutoff, intervalSince).PipeTo(
+            sender,
+            success: response => response,
+            failure: ex => new PerNodeSiteCallKpiResponse(
+                request.CorrelationId,
+                Success: false,
+                ErrorMessage: ex.GetBaseException().Message,
+                Nodes: Array.Empty<SiteCallNodeKpiSnapshot>()));
+    }
+
+    private async Task<PerNodeSiteCallKpiResponse> PerNodeKpiAsync(
+        string correlationId, DateTime stuckCutoff, DateTime intervalSince)
+    {
+        var (scope, repository) = ResolveRepository();
+        try
+        {
+            var nodes = await repository
+                .ComputePerNodeKpisAsync(stuckCutoff, intervalSince)
+                .ConfigureAwait(false);
+
+            return new PerNodeSiteCallKpiResponse(
+                correlationId, Success: true, ErrorMessage: null, nodes);
+        }
+        finally
+        {
+            scope?.Dispose();
+        }
+    }
+
     // ── Task 5: central→site Retry/Discard relay ──
 
     /// <summary>