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/Security/Authorization/GatewayRequestIdentityAccessor.cs

@@ -6,12 +6,10 @@ public sealed class GatewayRequestIdentityAccessor : IGatewayRequestIdentityAcce
 {
     private readonly AsyncLocal<ApiKeyIdentity?> currentIdentity = new();
 
-    /// <summary>Gets the current request identity.</summary>
+    /// <inheritdoc />
     public ApiKeyIdentity? Current => currentIdentity.Value;
 
-    /// <summary>Sets the current identity and returns a scope that restores the previous identity.</summary>
-    /// <param name="identity">The identity to push.</param>
-    /// <returns>Disposable scope.</returns>
+    /// <inheritdoc />
     public IDisposable Push(ApiKeyIdentity identity)
     {
         ArgumentNullException.ThrowIfNull(identity);