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/Core/ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests/FakeUpstream.cs

@@ -4,19 +4,29 @@ using ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
 
 namespace ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms.Tests;
 
+/// <summary>Test fake implementation of <see cref="ITagUpstreamSource"/> for verifying subscription behavior.</summary>
 public sealed class FakeUpstream : ITagUpstreamSource
 {
     private readonly ConcurrentDictionary<string, DataValueSnapshot> _values = new(StringComparer.Ordinal);
     private readonly ConcurrentDictionary<string, List<Action<string, DataValueSnapshot>>> _subs
         = new(StringComparer.Ordinal);
+    /// <summary>Gets the current count of active subscriptions.</summary>
     public int ActiveSubscriptionCount { get; private set; }
 
+    /// <summary>Sets a tag value without notifying subscribers.</summary>
+    /// <param name="path">The tag path to set.</param>
+    /// <param name="value">The value to set for the tag.</param>
+    /// <param name="statusCode">The OPC UA status code for the value.</param>
     public void Set(string path, object? value, uint statusCode = 0u)
     {
         var now = DateTime.UtcNow;
         _values[path] = new DataValueSnapshot(value, statusCode, now, now);
     }
 
+    /// <summary>Sets a tag value and notifies all current subscribers.</summary>
+    /// <param name="path">The tag path to set.</param>
+    /// <param name="value">The value to set for the tag.</param>
+    /// <param name="statusCode">The OPC UA status code for the value.</param>
     public void Push(string path, object? value, uint statusCode = 0u)
     {
         Set(path, value, statusCode);
@@ -28,10 +38,15 @@ public sealed class FakeUpstream : ITagUpstreamSource
         }
     }
 
+    /// <summary>Reads the current value of a tag, or returns a bad-status snapshot if not set.</summary>
+    /// <param name="path">The tag path to read.</param>
     public DataValueSnapshot ReadTag(string path)
         => _values.TryGetValue(path, out var v) ? v
             : new DataValueSnapshot(null, 0x80340000u, null, DateTime.UtcNow);
 
+    /// <summary>Subscribes an observer to tag changes for the given path.</summary>
+    /// <param name="path">The tag path to subscribe to.</param>
+    /// <param name="observer">The observer callback to invoke on tag changes.</param>
     public IDisposable SubscribeTag(string path, Action<string, DataValueSnapshot> observer)
     {
         var list = _subs.GetOrAdd(path, _ => []);
@@ -40,13 +55,19 @@ public sealed class FakeUpstream : ITagUpstreamSource
         return new Unsub(this, path, observer);
     }
 
+    /// <summary>Disposable subscription handle that unsubscribes the observer when disposed.</summary>
     private sealed class Unsub : IDisposable
     {
         private readonly FakeUpstream _up;
         private readonly string _path;
         private readonly Action<string, DataValueSnapshot> _observer;
+        /// <summary>Initializes the unsubscription handle with references needed to clean up the subscription.</summary>
+        /// <param name="up">The upstream source containing the subscription list.</param>
+        /// <param name="path">The tag path to unsubscribe from.</param>
+        /// <param name="observer">The observer to remove from the subscription list.</param>
         public Unsub(FakeUpstream up, string path, Action<string, DataValueSnapshot> observer)
         { _up = up; _path = path; _observer = observer; }
+        /// <summary>Removes the observer from the subscription list.</summary>
         public void Dispose()
         {
             if (_up._subs.TryGetValue(_path, out var list))