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.ControlPlane.Tests/RedundancyStateActorTests.cs

@@ -15,6 +15,7 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;
 /// </summary>
 public sealed class RedundancyStateActorTests : ControlPlaneActorTestBase
 {
+    /// <summary>Verifies that a self-join event triggers RedundancyStateChanged through the broadcast override.</summary>
     [Fact]
     public void Self_join_triggers_RedundancyStateChanged_via_broadcast_override()
     {
@@ -27,6 +28,7 @@ public sealed class RedundancyStateActorTests : ControlPlaneActorTestBase
         msg.CorrelationId.Value.ShouldNotBe(Guid.Empty);
     }
 
+    /// <summary>Verifies that multiple back-to-back events debounce to a single RedundancyStateChanged publication.</summary>
     [Fact]
     public void Multiple_back_to_back_events_debounce_to_single_publish()
     {