fix(telemetry): export the Galaxy driver's spans and galaxy.events.* counters (#892)

ZbTelemetryOptions.Meters/ActivitySources are strict allowlists. The host named only
ZB.MOM.WW.OtOpcUa and the LocalDb meter, so the in-process Galaxy driver's galaxy.* spans
and its event pump's galaxy.events.* counters (both on "ZB.MOM.WW.OtOpcUa.Driver.Galaxy")
were silently dropped from /metrics and OTLP. Found exercising OTLP end to end against a
collector (scadaproj#13).

- Galaxy driver: public GalaxyDriverTelemetryNames (MeterName / ActivitySourceName);
  GalaxyTelemetry and EventPump reference it.
- Host: ObservabilityExtensions.ObservedMeters / ObservedActivitySources include it.
- Host.IntegrationTests: ObservabilityAllowlistTests assert on the listener side (span
  sampled, instrument enabled) with an unregistered-name negative control; dropping the
  Galaxy entries fails 3 of 8.

Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi

src/Server/ZB.MOM.WW.OtOpcUa.Host/Observability/ObservabilityExtensions.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.Configuration;
 using ZB.MOM.WW.LocalDb.Replication;
 using ZB.MOM.WW.OtOpcUa.Commons.Observability;
+using ZB.MOM.WW.OtOpcUa.Driver.Galaxy;
 using ZB.MOM.WW.Telemetry;
 
 namespace ZB.MOM.WW.OtOpcUa.Host.Observability;
@@ -14,6 +15,31 @@ namespace ZB.MOM.WW.OtOpcUa.Host.Observability;
 /// </summary>
 public static class ObservabilityExtensions
 {
+    /// <summary>
+    /// Every meter the host exports. <c>ZbTelemetryOptions.Meters</c> is a STRICT allowlist (no
+    /// wildcard): the LocalDb replication meter publishes its <c>localdb.sync.*</c> /
+    /// <c>localdb.oplog.depth</c> series on driver nodes, and the in-process Galaxy driver its
+    /// <c>galaxy.events.*</c> counters — each is silently absent from <c>/metrics</c> and OTLP unless
+    /// named here. Adding a meter anywhere in the product means adding it here.
+    /// </summary>
+    public static readonly string[] ObservedMeters =
+    [
+        OtOpcUaTelemetry.MeterName,
+        LocalDbMetrics.MeterName,
+        GalaxyDriverTelemetryNames.MeterName,
+    ];
+
+    /// <summary>
+    /// Every activity source the host exports over OTLP. Also a strict allowlist: the Galaxy
+    /// driver's <c>galaxy.*</c> gateway-call spans were dropped until scadaproj#13 because its source
+    /// was missing here.
+    /// </summary>
+    public static readonly string[] ObservedActivitySources =
+    [
+        OtOpcUaTelemetry.ActivitySourceName,
+        GalaxyDriverTelemetryNames.ActivitySourceName,
+    ];
+
     /// <summary>Adds OtOpcUa observability (metrics and tracing) to the service collection.</summary>
     /// <param name="services">The service collection to add observability services to.</param>
     /// <param name="configuration">
@@ -28,12 +54,9 @@ public static class ObservabilityExtensions
         return services.AddZbTelemetry(o =>
         {
             o.ServiceName = "otopcua";
-            // o.Meters is a STRICT allowlist — ZbTelemetry adds only the named meters, with no
-            // wildcard. The LocalDb replication engine publishes under its own meter name, so
-            // without this entry its localdb.sync.* / localdb.oplog.depth series are silently absent
-            // from /metrics on driver nodes (the exact omission a ScadaBridge live gate caught).
-            o.Meters = [OtOpcUaTelemetry.MeterName, LocalDbMetrics.MeterName];
-            o.ActivitySources = [OtOpcUaTelemetry.ActivitySourceName];
+            // Strict allowlists — see ObservedMeters / ObservedActivitySources.
+            o.Meters = ObservedMeters;
+            o.ActivitySources = ObservedActivitySources;
             if (Enum.TryParse<ZbExporter>(configuration["OtOpcUa:Telemetry:Exporter"], ignoreCase: true, out var exporter))
                 o.Exporter = exporter;
             var otlp = configuration["OtOpcUa:Telemetry:OtlpEndpoint"];