docs: backfill XML documentation across 756 files

Adds <summary>, <param>, <typeparam>, and <inheritdoc/> tags to public
members surfaced by commentchecker — resolves 5,847 of 5,869 issues
(99.6%) across three /fixdocs passes.

tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/OpcUaApplicationHostTests.cs

@@ -18,6 +18,7 @@ public sealed class OpcUaApplicationHostTests : IDisposable
         Path.GetTempPath(),
         $"otopcua-pki-{Guid.NewGuid():N}");
 
+    /// <summary>Verifies StartAsync creates a self-signed certificate in the PKI own store.</summary>
     [Fact]
     public async Task StartAsync_creates_application_certificate_in_pki_own()
     {
@@ -39,6 +40,7 @@ public sealed class OpcUaApplicationHostTests : IDisposable
         Directory.EnumerateFiles(ownCerts).ShouldNotBeEmpty("expected a self-signed cert file in the own store");
     }
 
+    /// <summary>Verifies StartAsync reuses an existing certificate on the second boot.</summary>
     [Fact]
     public async Task StartAsync_reuses_existing_certificate_on_second_boot()
     {
@@ -89,6 +91,7 @@ public sealed class OpcUaApplicationHostTests : IDisposable
         return port;
     }
 
+    /// <summary>Cleans up the temporary PKI directory.</summary>
     public void Dispose()
     {
         if (Directory.Exists(_pkiRoot))