docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/IOpcUaClient.cs

@@ -89,6 +89,11 @@ public interface IOpcUaClient : IAsyncDisposable
     /// active conditions as Snapshot…SnapshotComplete transitions. Returns a
     /// handle for <see cref="RemoveAlarmSubscriptionAsync"/>.
     /// </summary>
+    /// <param name="sourceNodeId">OPC UA node ID to monitor; null subscribes to the Server object.</param>
+    /// <param name="conditionFilter">Optional OPC UA condition type filter; null subscribes to all conditions.</param>
+    /// <param name="onTransition">Callback invoked for each alarm transition received from the server.</param>
+    /// <param name="cancellationToken">Token to observe for cancellation.</param>
+    /// <returns>A task that resolves to a subscription handle string for use with <see cref="RemoveAlarmSubscriptionAsync"/>.</returns>
     Task<string> CreateAlarmSubscriptionAsync(
         string? sourceNodeId,
         string? conditionFilter,
@@ -96,6 +101,9 @@ public interface IOpcUaClient : IAsyncDisposable
         CancellationToken cancellationToken = default);
 
     /// <summary>Removes an alarm-event subscription by handle.</summary>
+    /// <param name="subscriptionHandle">The handle returned by <see cref="CreateAlarmSubscriptionAsync"/>.</param>
+    /// <param name="cancellationToken">Token to observe for cancellation.</param>
+    /// <returns>A task representing the asynchronous operation.</returns>
     Task RemoveAlarmSubscriptionAsync(string subscriptionHandle, CancellationToken cancellationToken = default);
 
     /// <summary>
@@ -167,7 +175,7 @@ internal class StubOpcUaClient : IOpcUaClient
     /// <inheritdoc />
     public bool IsConnected { get; private set; }
 #pragma warning disable CS0067
-    /// <inheritdoc />
+    /// <summary>Raised when the OPC UA session detects a keep-alive failure or the server becomes unreachable.</summary>
     public event Action? ConnectionLost;
 #pragma warning restore CS0067
 
@@ -230,7 +238,8 @@ internal class StubOpcUaClient : IOpcUaClient
         string? parentNodeId, CancellationToken cancellationToken = default)
         => throw new NotImplementedException();
 
-    /// <inheritdoc />
+    /// <summary>Disposes this stub client and marks the connection as closed.</summary>
+    /// <returns>A completed <see cref="ValueTask"/>.</returns>
     public ValueTask DisposeAsync()
     {
         IsConnected = false;