refactor: keep the gs_usb option out of non-Windows builds

The radio button was only disabled elsewhere, which advertised a connection
type that platform can never offer. Hide it instead, and guard the gs_usb.h
include so nothing outside Windows reaches for it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XZnuZJ7zc3e8hk6C8bGDZN

connections/canconfactory.cpp

@@ -7,7 +7,9 @@
 #include "lawicel_serial.h"
 #include "canserver.h"
 #include "canlogserver.h"
+#ifdef Q_OS_WIN
 #include "gs_usb.h"
+#endif
 
 using namespace CANCon;
 

connections/newconnectiondialog.cpp

@@ -37,9 +37,9 @@ NewConnectionDialog::NewConnectionDialog(QVector<QString>* gvretips, QVector<QSt
     connect(ui->rbGSUSB, &QAbstractButton::clicked, this, &NewConnectionDialog::handleConnTypeChanged);
 
 #ifndef Q_OS_WIN
-    //on Linux and macOS the kernel gs_usb driver already exposes these devices as SocketCAN
-    ui->rbGSUSB->setEnabled(false);
-    ui->rbGSUSB->setToolTip("Connect gs_usb devices through SocketCAN on this platform");
+    //on Linux and macOS the kernel gs_usb driver already exposes these devices as SocketCAN,
+    //so there is nothing here to offer and the option is left out entirely
+    ui->rbGSUSB->setVisible(false);
 #endif
 
     connect(ui->cbDeviceType, QOverload<int>::of(&QComboBox::currentIndexChanged), this, &NewConnectionDialog::handleDeviceTypeChanged);