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.

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Security/IOpcUaUserAuthenticator.cs

@@ -17,6 +17,10 @@ public interface IOpcUaUserAuthenticator
     /// reject codes, and a thrown exception escapes into the OPC UA SDK's session-activation
     /// path where it surfaces as a generic <c>BadInternalError</c>.
     /// </summary>
+    /// <param name="username">The username to authenticate.</param>
+    /// <param name="password">The cleartext password to authenticate.</param>
+    /// <param name="ct">The cancellation token.</param>
+    /// <returns>An OpcUaUserAuthResult indicating success or failure.</returns>
     Task<OpcUaUserAuthResult> AuthenticateUserNameAsync(string username, string password, CancellationToken ct);
 }
 
@@ -27,9 +31,16 @@ public sealed record OpcUaUserAuthResult(
     IReadOnlyList<string> Roles,
     string? Error)
 {
+    /// <summary>Creates a successful authentication result with the specified display name and roles.</summary>
+    /// <param name="displayName">The display name for the authenticated user.</param>
+    /// <param name="roles">The roles to assign to the authenticated user.</param>
+    /// <returns>A successful OpcUaUserAuthResult.</returns>
     public static OpcUaUserAuthResult Allow(string displayName, IReadOnlyList<string> roles) =>
         new(true, displayName, roles, null);
 
+    /// <summary>Creates a failed authentication result with the specified error message.</summary>
+    /// <param name="error">The error message describing why authentication failed.</param>
+    /// <returns>A failed OpcUaUserAuthResult.</returns>
     public static OpcUaUserAuthResult Deny(string error) =>
         new(false, null, Array.Empty<string>(), error);
 }
@@ -44,6 +55,11 @@ public sealed class NullOpcUaUserAuthenticator : IOpcUaUserAuthenticator
     public static readonly NullOpcUaUserAuthenticator Instance = new();
     private NullOpcUaUserAuthenticator() { }
 
+    /// <summary>Authenticates a username (always denies in this null implementation).</summary>
+    /// <param name="username">The username to authenticate.</param>
+    /// <param name="password">The cleartext password to authenticate.</param>
+    /// <param name="ct">The cancellation token.</param>
+    /// <returns>A task that returns a denial result indicating no authenticator is configured.</returns>
     public Task<OpcUaUserAuthResult> AuthenticateUserNameAsync(string username, string password, CancellationToken ct) =>
         Task.FromResult(OpcUaUserAuthResult.Deny("No UserName authenticator is configured on this server."));
 }