Expand XML docs across bridge and test code

src/ZB.MOM.WW.LmxOpcUa.Host/Domain/ConnectionStateChangedEventArgs.cs

@@ -7,10 +7,27 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Domain
     /// </summary>
     public class ConnectionStateChangedEventArgs : EventArgs
     {
+        /// <summary>
+        /// Gets the previous MXAccess connection state before the transition was raised.
+        /// </summary>
         public ConnectionState PreviousState { get; }
+
+        /// <summary>
+        /// Gets the new MXAccess connection state that the bridge moved into.
+        /// </summary>
         public ConnectionState CurrentState { get; }
+
+        /// <summary>
+        /// Gets an operator-facing message that explains why the connection state changed.
+        /// </summary>
         public string Message { get; }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ConnectionStateChangedEventArgs"/> class.
+        /// </summary>
+        /// <param name="previous">The connection state being exited.</param>
+        /// <param name="current">The connection state being entered.</param>
+        /// <param name="message">Additional context about the transition, such as a connection fault or reconnect attempt.</param>
         public ConnectionStateChangedEventArgs(ConnectionState previous, ConnectionState current, string message = "")
         {
             PreviousState = previous;