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/Phase7ApplierHierarchyTests.cs

@@ -22,6 +22,7 @@ public sealed class Phase7ApplierHierarchyTests : IDisposable
         Path.GetTempPath(),
         $"otopcua-pki-{Guid.NewGuid():N}");
 
+    /// <summary>Verifies that MaterialiseHierarchy creates areas, lines, and equipment with correct parent relationships.</summary>
     [Fact]
     public void MaterialiseHierarchy_creates_areas_then_lines_then_equipment_with_correct_parents()
     {
@@ -44,6 +45,7 @@ public sealed class Phase7ApplierHierarchyTests : IDisposable
         calls[2].ShouldBe(("eq-1", "line-1", "Pump-1"));
     }
 
+    /// <summary>Verifies that orphan equipment without a parent line appears under root.</summary>
     [Fact]
     public void MaterialiseHierarchy_orphan_equipment_hangs_under_root()
     {
@@ -62,6 +64,7 @@ public sealed class Phase7ApplierHierarchyTests : IDisposable
         sink.Calls.Single().ShouldBe(("eq-orphan", null, "Orphan"));
     }
 
+    /// <summary>Verifies that MaterialiseHierarchy creates folder nodes in a real SDK node manager.</summary>
     [Fact]
     public async Task MaterialiseHierarchy_against_real_SDK_node_manager_creates_folder_nodes()
     {
@@ -112,6 +115,7 @@ public sealed class Phase7ApplierHierarchyTests : IDisposable
         return port;
     }
 
+    /// <summary>Disposes of resources allocated by this test class.</summary>
     public void Dispose()
     {
         if (Directory.Exists(_pkiRoot))
@@ -124,12 +128,28 @@ public sealed class Phase7ApplierHierarchyTests : IDisposable
     private sealed class RecordingFolderSink : IOpcUaAddressSpaceSink
     {
         private readonly ConcurrentQueue<(string NodeId, string? Parent, string DisplayName)> _calls = new();
+        /// <summary>Gets the list of EnsureFolder calls recorded by this sink.</summary>
         public List<(string NodeId, string? Parent, string DisplayName)> Calls => _calls.ToList();
 
+        /// <summary>Records a value write (stub implementation for testing).</summary>
+        /// <param name="nodeId">The node ID of the variable.</param>
+        /// <param name="value">The value to write.</param>
+        /// <param name="quality">The OPC UA quality value.</param>
+        /// <param name="sourceTimestampUtc">The source timestamp in UTC.</param>
         public void WriteValue(string nodeId, object? value, OpcUaQuality quality, DateTime sourceTimestampUtc) { }
+        /// <summary>Records an alarm state write (stub implementation for testing).</summary>
+        /// <param name="alarmNodeId">The node ID of the alarm condition.</param>
+        /// <param name="active">Whether the alarm is active.</param>
+        /// <param name="acknowledged">Whether the alarm has been acknowledged.</param>
+        /// <param name="sourceTimestampUtc">The source timestamp in UTC.</param>
         public void WriteAlarmState(string alarmNodeId, bool active, bool acknowledged, DateTime sourceTimestampUtc) { }
+        /// <summary>Records a folder creation request.</summary>
+        /// <param name="folderNodeId">The node ID of the folder.</param>
+        /// <param name="parentNodeId">The node ID of the parent folder, or null for root.</param>
+        /// <param name="displayName">The display name of the folder.</param>
         public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName)
             => _calls.Enqueue((folderNodeId, parentNodeId, displayName));
+        /// <summary>Rebuilds the address space (stub implementation for testing).</summary>
         public void RebuildAddressSpace() { }
     }
 }