chore: scaffold CMake build system

Add the CMake build for the Swift + C++ macOS port, mirroring the
refix layout: deps/ modules (Platform, Flags, Sanitizers, FindUnity),
per-module static libraries (usb, auth, mt76, gip, hid, api), a Swift
app entry point with a pure C bridge header, and a Unity test suite
behind BUILD_TESTING.

Swift requires the Ninja or Xcode generator; a guard in
CMakeLists.txt rejects anything else.

Co-Authored-By: qwen (qwen/qwen3.8-27b@q2_k_xl): scaffolded CMake build + tests

src/app/api.cpp

@@ -0,0 +1,19 @@
+// C ABI bridge between the C++ protocol stack and the Swift app layer.
+
+#include "app/xone_api.h"
+
+#include "usb/usb_transport.hpp"
+
+#ifndef XONE_VERSION
+#define XONE_VERSION "0.1.0"
+#endif
+
+extern "C" const char *xone_version(void)
+{
+    return XONE_VERSION;
+}
+
+extern "C" bool xone_dongle_present(void)
+{
+    return xone::usb::probe();
+}

src/app/main.swift

@@ -0,0 +1,13 @@
+// xone_macos — macOS app entry point (Swift)
+// TODO(phase 5): device discovery, pairing UI, status display, menubar icon.
+
+import Foundation
+
+let version = String(cString: xone_version())
+print("xone_macos \(version)")
+
+if xone_dongle_present() {
+    print("Xbox Wireless Dongle detected")
+} else {
+    print("No Xbox Wireless Dongle detected (plug in the dongle and retry)")
+}

src/auth/crypto.cpp

@@ -0,0 +1,7 @@
+// Auth + crypto
+// TODO(phase 1): port from medusalix/xone auth/auth.c + auth/crypto.c.
+
+#include "auth/crypto.hpp"
+
+namespace xone::auth {
+} // namespace xone::auth

src/gip/protocol.cpp

@@ -0,0 +1,7 @@
+// GIP protocol (Game Input Protocol)
+// TODO(phase 1): port from medusalix/xone bus/protocol.c + bus/bus.c.
+
+#include "gip/protocol.hpp"
+
+namespace xone::gip {
+} // namespace xone::gip

src/hid/hid_device.cpp

@@ -0,0 +1,7 @@
+// Virtual HID gamepad presentation
+// TODO(phase 4): DriverKit IOHIDDriver implementation.
+
+#include "hid/hid_device.hpp"
+
+namespace xone::hid {
+} // namespace xone::hid

src/mt76/mt76.cpp

@@ -0,0 +1,16 @@
+// MT76 chip protocol (MediaTek MT76xx radio in the dongle)
+// TODO(phase 3): port from medusalix/xone transport/mt76.c.
+
+#include "mt76/mt76.hpp"
+
+namespace xone::mt76 {
+
+auto load_firmware(std::uint16_t pid, char const *firmware_path) -> bool
+{
+    (void)pid;
+    (void)firmware_path;
+    // Not implemented yet: no USB transport in place.
+    return false;
+}
+
+} // namespace xone::mt76

src/usb/usb_transport.cpp

@@ -0,0 +1,14 @@
+// USB transport (IOKit / IOUSBFamily)
+// TODO(phase 2): port from medusalix/xone transport/dongle.c + mt76.c USB calls.
+
+#include "usb/usb_transport.hpp"
+
+namespace xone::usb {
+
+auto probe() -> bool
+{
+    // Not implemented yet: no IOKit device matching in place.
+    return false;
+}
+
+} // namespace xone::usb