docs(xmldoc): fill missing XML docs + strip tracking-ID comments across src

Adds <summary>/<param>/<returns>/<inheritdoc> where missing and removes
project bookkeeping IDs (task/tracking refs) from shipped code comments,
so the docs read cleanly and CommentChecker is quiet except for known
false positives (PLC/protocol terms, event/IEqualityComparer inheritdoc).
Doc/comment-only; no logic changed; solution builds clean.

src/Core/ZB.MOM.WW.OtOpcUa.Commons/Observability/OtOpcUaTelemetry.cs

@@ -69,6 +69,7 @@ public static class OtOpcUaTelemetry
     /// null when no listener is attached so the call site stays cheap on undecorated builds.
     /// </summary>
     /// <param name="deploymentId">The deployment identifier to tag the span with.</param>
+    /// <returns>The started activity, or <c>null</c> when no listener is attached.</returns>
     public static Activity? StartDeployApplySpan(string deploymentId)
     {
         var activity = ActivitySource.StartActivity("otopcua.deploy.apply", ActivityKind.Internal);
@@ -77,6 +78,7 @@ public static class OtOpcUaTelemetry
     }
 
     /// <summary>Span wrapping a full OPC UA address-space rebuild (AddressSpace plan → apply).</summary>
+    /// <returns>The started activity, or <c>null</c> when no listener is attached.</returns>
     public static Activity? StartAddressSpaceRebuildSpan()
         => ActivitySource.StartActivity("otopcua.opcua.address_space_rebuild", ActivityKind.Internal);
 }