docs(src): add missing XML docs and strip tracking-ID comments

Sweep of 203 source files resolving CommentChecker findings: add
<summary>/<param>/<returns>/<inheritdoc> where missing, and remove
resolved task/issue tracking markers (Tests-NNN, Worker-NNN, Server-NNN,
Task N) from code comments. Comment/doc-only — no logic changes.
Server+Tests build clean under TreatWarningsAsErrors.

src/ZB.MOM.WW.MxGateway.Server/Metrics/GatewayMetrics.cs

@@ -89,7 +89,7 @@ public sealed class GatewayMetrics : IDisposable
     /// (via <c>InternalsVisibleTo</c>) so a <see cref="MeterListener"/> can filter measurements by
     /// <see cref="object.ReferenceEquals"/> against this specific instance rather than by the
     /// process-shared <see cref="MeterName"/>, which would cross-talk between parallel tests that
-    /// each build their own <see cref="GatewayMetrics"/> (Tests-027).
+    /// each build their own <see cref="GatewayMetrics"/>.
     /// </summary>
     internal Meter Meter => _meter;
 
@@ -413,6 +413,7 @@ public sealed class GatewayMetrics : IDisposable
     };
 
     /// <summary>Sets the current alarm provider-mode gauge without recording a switch (e.g. startup baseline).</summary>
+    /// <param name="mode">The alarm provider mode value to record.</param>
     public void SetAlarmProviderMode(int mode)
     {
         lock (_syncRoot) { _alarmProviderMode = mode; }
@@ -421,6 +422,7 @@ public sealed class GatewayMetrics : IDisposable
     /// <summary>
     /// Returns a snapshot of all current metric values.
     /// </summary>
+    /// <returns>The current metrics snapshot.</returns>
     public GatewayMetricsSnapshot GetSnapshot()
     {
         lock (_syncRoot)