feat(lmxproxy): phase 1 — v2 protocol types and domain model

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/src-reference/ZB.MOM.WW.LmxProxy.Client/Domain/ConnectionState.cs

@@ -0,0 +1,49 @@
+using System;
+
+namespace ZB.MOM.WW.LmxProxy.Client.Domain;
+
+/// <summary>
+/// Represents the connection state of an LmxProxy client.
+/// </summary>
+public enum ConnectionState
+{
+	/// <summary>Not connected to the server.</summary>
+	Disconnected,
+
+	/// <summary>Connection attempt in progress.</summary>
+	Connecting,
+
+	/// <summary>Connected and ready for operations.</summary>
+	Connected,
+
+	/// <summary>Graceful disconnect in progress.</summary>
+	Disconnecting,
+
+	/// <summary>Connection failed with an error.</summary>
+	Error,
+
+	/// <summary>Attempting to re-establish a lost connection.</summary>
+	Reconnecting
+}
+
+/// <summary>
+/// Event arguments for connection state change notifications.
+/// </summary>
+public class ConnectionStateChangedEventArgs : EventArgs
+{
+	/// <summary>The previous connection state.</summary>
+	public ConnectionState OldState { get; }
+
+	/// <summary>The new connection state.</summary>
+	public ConnectionState NewState { get; }
+
+	/// <summary>Optional message describing the state change (e.g., error details).</summary>
+	public string? Message { get; }
+
+	public ConnectionStateChangedEventArgs(ConnectionState oldState, ConnectionState newState, string? message = null)
+	{
+		OldState = oldState;
+		NewState = newState;
+		Message = message;
+	}
+}