perf(ui): shared KPI cache, live-cache-backed alarm summary, coalesced debug renders

src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/AlarmSummaryService.cs

@@ -128,7 +128,20 @@ public sealed class AlarmSummaryService : IAlarmSummaryService
     }
 
     /// <inheritdoc/>
-    public AlarmSummaryResult BuildFromLiveAlarms(IReadOnlyList<AlarmStateChanged> alarms)
+    public AlarmSummaryResult BuildFromLiveAlarms(IReadOnlyList<AlarmStateChanged> alarms) =>
+        BuildFromLiveAlarmsCore(alarms);
+
+    /// <inheritdoc/>
+    public AlarmRollup ComputeRollup(IReadOnlyList<AlarmSummaryRow> rows) => ComputeRollupCore(rows);
+
+    /// <summary>
+    /// Pure flattening of a live-cache snapshot into summary rows. Shared with
+    /// <see cref="SharedAlarmSummaryService"/>, which memoizes the fan-out but must produce
+    /// byte-identical rows on the live path — one implementation, no drift.
+    /// </summary>
+    /// <param name="alarms">The live-cache alarm snapshot.</param>
+    /// <returns>The flattened, deterministically ordered rows (never any not-reporting names).</returns>
+    internal static AlarmSummaryResult BuildFromLiveAlarmsCore(IReadOnlyList<AlarmStateChanged> alarms)
     {
         ArgumentNullException.ThrowIfNull(alarms);
 
@@ -147,8 +160,14 @@ public sealed class AlarmSummaryService : IAlarmSummaryService
         return new AlarmSummaryResult(orderedRows, Array.Empty<string>());
     }
 
-    /// <inheritdoc/>
-    public AlarmRollup ComputeRollup(IReadOnlyList<AlarmSummaryRow> rows)
+    /// <summary>
+    /// Pure roll-up over already-flattened rows. Shared with
+    /// <see cref="SharedAlarmSummaryService"/> for the same one-implementation reason as
+    /// <see cref="BuildFromLiveAlarmsCore"/>.
+    /// </summary>
+    /// <param name="rows">The rows to roll up.</param>
+    /// <returns>The active/worst-severity/unacked/by-kind roll-up.</returns>
+    internal static AlarmRollup ComputeRollupCore(IReadOnlyList<AlarmSummaryRow> rows)
     {
         ArgumentNullException.ThrowIfNull(rows);