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.Runtime.Tests/Harness/RuntimeActorTestBase.cs

@@ -11,6 +11,7 @@ namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;
 /// </summary>
 public abstract class RuntimeActorTestBase : TestKit
 {
+    /// <summary>Gets the Akka test HOCON configuration string for single-node cluster setup.</summary>
     protected static string AkkaTestHocon => @"
 akka {
     loglevel = ""WARNING""
@@ -32,6 +33,7 @@ akka {
     }
 }";
 
+    /// <summary>Initializes a new instance of the RuntimeActorTestBase class with Akka test setup.</summary>
     protected RuntimeActorTestBase() : base(AkkaTestHocon)
     {
         var cluster = Akka.Cluster.Cluster.Get(Sys);
@@ -40,6 +42,9 @@ akka {
             TimeSpan.FromSeconds(5));
     }
 
+    /// <summary>Creates a new in-memory database factory for testing.</summary>
+    /// <param name="dbName">The database name, or null to generate a unique name.</param>
+    /// <returns>An IDbContextFactory for the in-memory database.</returns>
     protected static IDbContextFactory<OtOpcUaConfigDbContext> NewInMemoryDbFactory(string? dbName = null)
     {
         dbName ??= Guid.NewGuid().ToString("N");
@@ -48,6 +53,8 @@ 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>()