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.Tests/Gateway/GatewayTlsBootstrapTests.cs

@@ -21,6 +21,7 @@ public sealed class GatewayTlsBootstrapTests
     /// trusted dev cert, Kestrel would otherwise serve that dev cert (<c>CN=localhost</c>), so the
     /// subject assertion is what makes this test fail without the wiring on either kind of host.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Host_ServesGeneratedCertificate_WhenHttpsEndpointHasNoCertificate()
     {