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

include/usb/usb_transport.hpp

@@ -0,0 +1,25 @@
+#pragma once
+
+// ==============================================================================
+// USB transport (IOKit / IOUSBFamily)
+// ==============================================================================
+// Owns the physical Xbox Wireless Dongle:
+//   VID 0x045E, PIDs 0x02E6 (old), 0x02FE (new), 0x02F9 (ASUS/Lenovo built-in),
+//   0x091E (Surface Book 2).
+//
+// Port target: medusalix/xone transport/dongle.c + transport/mt76.c USB calls.
+// Linux usb_control_msg()/usb_bulk_msg() map to IOUSBDeviceInterface
+// DeviceRequest / IOUSBInterfaceInterface WritePipe+ReadPipe.
+// ==============================================================================
+
+#include <cstdint>
+
+namespace xone::usb {
+
+// Probe for a connected dongle and claim its WLAN interface
+// (bInterfaceNumber 1).
+// TODO(phase 2): IOKit implementation (IOServiceMatching, interface open,
+// EP 0x04 bulk in/out + EP 0x05 interrupt in).
+auto probe() -> bool;
+
+} // namespace xone::usb