XPL2 protocol foundation: wire framing, typed API, KA_PING, GS_JC_VERSION

Add Xpl2Protocol namespace with buildMessage/parseMessage for wire
serialization. Replace raw send/receive API on Xpl2Client with typed
protocol methods and internal dispatch. Auto-reply to KA_PING on all
sockets (qDebug only). Add GS_JC_VERSION as first typed command with
controllerId, firmwareVersion, hardwareVersion, printheadCount properties.

Upgrade mock server from echo to line-based command dispatch with 1s
KA_PING timer and canned GS_JC_VERSION response. Unknown commands
produce qWarning instead of echo.

Overhaul demo: remove raw send UI and port config, add wireDebug
toggle and Get JC Version button.

1 files changed, 11 insertions, 2 deletions

diff --git a/mock-server/EchoServer.h b/mock-server/EchoServer.h
index 2e51b1e..c0a41c9 100644
--- a/mock-server/EchoServer.h
+++ b/mock-server/EchoServer.h
@@ -1,10 +1,14 @@
 /**
  * @file   EchoServer.h
- * @brief  Simple TCP echo server for a single port.
+ * @brief  Mock XPL2 server for a single port.
  */
 #pragma once
 
+#include <QList>
 #include <QTcpServer>
+#include <QTimer>
+
+class QTcpSocket;
 
 class EchoServer : public QTcpServer
 {
@@ -15,10 +19,15 @@ public:
 
 private slots:
   void onNewConnection ();
-  void onClientReadyRead ();
+  void onClientMessageReady ();
   void onClientDisconnected ();
+  void sendKaPing ();
 
 private:
+  void handleCommand (QTcpSocket *client, const QByteArray &line);
+
   const char *m_name;
   quint16 m_port;
+  QList<QTcpSocket *> m_clients;
+  QTimer m_pingTimer;
 };