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/Harness/ControlPlaneTestHarness.cs

@@ -16,6 +16,7 @@ namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Harness;
 /// </summary>
 public abstract class ControlPlaneActorTestBase : TestKit
 {
+    /// <summary>Gets the Akka configuration for test actors, including cluster and pub-sub extensions.</summary>
     protected static string AkkaTestHocon => @"
 akka {
     loglevel = ""WARNING""
@@ -38,6 +39,7 @@ akka {
     }
 }";
 
+    /// <summary>Initializes a new instance of the test harness; joins the cluster and waits for up status.</summary>
     protected ControlPlaneActorTestBase() : base(AkkaTestHocon)
     {
         // Self-join so the cluster transitions to Up and DistributedPubSub forms.
@@ -47,6 +49,9 @@ akka {
             TimeSpan.FromSeconds(5));
     }
 
+    /// <summary>Creates a new in-memory database context factory with an optional database name.</summary>
+    /// <param name="dbName">Optional database name; defaults to a random GUID if not provided.</param>
+    /// <returns>A context factory for creating in-memory config database contexts.</returns>
     protected static IDbContextFactory<OtOpcUaConfigDbContext> NewInMemoryDbFactory(string? dbName = null)
     {
         dbName ??= Guid.NewGuid().ToString("N");
@@ -55,6 +60,8 @@ akka {
 
     private sealed class InMemoryConfigDbFactory(string dbName) : IDbContextFactory<OtOpcUaConfigDbContext>
     {
+        /// <summary>Creates a new in-memory database context.</summary>
+        /// <returns>A new OtOpcUaConfigDbContext instance.</returns>
         public OtOpcUaConfigDbContext CreateDbContext()
         {
             var opts = new DbContextOptionsBuilder<OtOpcUaConfigDbContext>()