feat(health): additive script-scheduler stats on ISiteHealthCollector + SiteHealthReport (S2/UA5)

src/ZB.MOM.WW.ScadaBridge.HealthMonitoring/ISiteHealthCollector.cs

@@ -141,6 +141,24 @@ public interface ISiteHealthCollector
         // SiteHealthCollector overrides this with the Interlocked.Exchange store.
     }
 
+    /// <summary>
+    /// Replace the latest script-execution-scheduler gauges (queue depth, busy
+    /// thread count, and age in seconds of the oldest in-flight script) used by
+    /// the next <see cref="CollectReport"/> call. Refreshed periodically by the
+    /// <c>ScriptSchedulerStatsReporter</c> hosted service. Point-in-time: the
+    /// values are NOT reset on <see cref="CollectReport"/>. S2/UA5 — surfaces a
+    /// saturated or stuck script-execution pool on the site health report.
+    /// Default interface implementation is a no-op so existing test fakes continue
+    /// to compile without per-fake updates.
+    /// </summary>
+    /// <param name="queueDepth">Script tasks waiting to run.</param>
+    /// <param name="busyThreads">Worker threads currently executing a script.</param>
+    /// <param name="oldestBusyAgeSeconds">Age (seconds) of the oldest in-flight script, or <c>null</c> when idle.</param>
+    void SetScriptSchedulerStats(int queueDepth, int busyThreads, double? oldestBusyAgeSeconds)
+    {
+        // Default no-op so test fakes do not need to be updated.
+    }
+
     /// <summary>
     /// Sets the hostname of this node.
     /// </summary>