fix(alarms): truncation-safe transitions; perf: single-pass alarm parse; configurable poll cadence

src/ZB.MOM.WW.MxGateway.Server/Configuration/AlarmsOptions.cs

@@ -46,6 +46,29 @@ public sealed class AlarmsOptions
     /// </summary>
     public int ReconcileIntervalSeconds { get; init; } = 30;
 
+    /// <summary>
+    ///     Cadence at which the worker's STA polls the AVEVA alarm consumer
+    ///     (<c>GetXmlCurrentAlarms2</c>) for the current active-alarm snapshot.
+    ///     Default 500 ms; must be at least 100 ms. Every poll is a COM call
+    ///     plus an XML parse on the STA that also serves reads and writes, so
+    ///     driving it below 100 ms starves the command path. Conveyed to the
+    ///     worker through the <c>MXGATEWAY_ALARM_POLL_INTERVAL_MS</c>
+    ///     environment variable.
+    /// </summary>
+    public int PollIntervalMilliseconds { get; init; } = 500;
+
+    /// <summary>
+    ///     Cap the worker passes to <c>GetXmlCurrentAlarms2</c>'s
+    ///     <c>maxAlmCnt</c> argument. Default 1024; must be at least 64. A
+    ///     fetch that comes back holding exactly this many records is treated
+    ///     as truncated: the worker keeps the alarms the capped fetch could
+    ///     not mention in its snapshot rather than letting their absence read
+    ///     as a clear. Raise it on galaxies whose steady-state active-alarm
+    ///     count approaches the cap. Conveyed to the worker through the
+    ///     <c>MXGATEWAY_ALARM_MAX_ALARMS_PER_FETCH</c> environment variable.
+    /// </summary>
+    public int MaxAlarmsPerFetch { get; init; } = 1024;
+
     /// <summary>
     ///     Configuration for the alarm-manager ↔ subtag fallback mechanism:
     ///     operating mode, failure-detection thresholds, discovery, and subtag