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/DeferredServiceLevelPublisherTests.cs

@@ -6,6 +6,7 @@ namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests;
 
 public sealed class DeferredServiceLevelPublisherTests
 {
+    /// <summary>Verifies that publish before SetInner is a safe no-op.</summary>
     [Fact]
     public void Publish_before_SetInner_is_a_safe_noop()
     {
@@ -14,6 +15,7 @@ public sealed class DeferredServiceLevelPublisherTests
         Should.NotThrow(() => deferred.Publish(123));
     }
 
+    /// <summary>Verifies that publish after SetInner routes to the inner publisher.</summary>
     [Fact]
     public void Publish_after_SetInner_routes_to_the_inner()
     {
@@ -26,6 +28,7 @@ public sealed class DeferredServiceLevelPublisherTests
         recording.LastValue.ShouldBe((byte)200);
     }
 
+    /// <summary>Verifies that SetInner with null reverts to the null publisher.</summary>
     [Fact]
     public void SetInner_null_reverts_to_Null_publisher()
     {
@@ -42,7 +45,10 @@ public sealed class DeferredServiceLevelPublisherTests
 
     private sealed class RecordingPublisher : IServiceLevelPublisher
     {
+        /// <summary>Gets the last published service level value.</summary>
         public byte? LastValue { get; private set; }
+        /// <summary>Publishes a service level value.</summary>
+        /// <param name="serviceLevel">The service level to publish.</param>
         public void Publish(byte serviceLevel) => LastValue = serviceLevel;
     }
 }