refactor(kpi): K2/K6/K7 review fixups — empty-batch guard + sealed repo + uniform TryAddEnumerable + KPI-age doc fidelity + coverage

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

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Kpi;
 using ZB.MOM.WW.ScadaBridge.SiteCallAudit.Kpi;
 
@@ -44,7 +45,9 @@ public static class ServiceCollectionExtensions
         // KPIs (global + per-site + per-node) into the KpiSample history store.
         // Scoped so each pass resolves a fresh ISiteCallAuditRepository scope,
         // mirroring the actor's scope-per-message repository access.
-        services.AddScoped<IKpiSampleSource, SiteCallAuditKpiSampleSource>();
+        // TryAddEnumerable is idempotent — no double-registration if AddSiteCallAudit
+        // is ever called more than once, matching the AuditLog (K8) idiom.
+        services.TryAddEnumerable(ServiceDescriptor.Scoped<IKpiSampleSource, SiteCallAuditKpiSampleSource>());
 
         return services;
     }