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

CMakeLists.txt

@@ -0,0 +1,107 @@
+# CMake supports Swift only with the Ninja and Xcode generators.
+if(NOT CMAKE_GENERATOR MATCHES "^(Ninja|Xcode)$")
+    message(FATAL_ERROR
+        "This project requires the Ninja or Xcode generator for Swift support.\n"
+        "  Configure with: cmake -S . -B build -G Ninja")
+endif()
+
+cmake_minimum_required(VERSION 3.21)
+project(xone_macos VERSION 0.1.0 LANGUAGES CXX Swift)
+
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+# Add the deps directory to the module path
+# Required for find_package injection
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/deps")
+
+# Platform and compiler detection
+include(Platform)
+include(Flags)
+include(Sanitizers)
+
+# ==============================================================================
+# Module libraries (bottom-up layering, mirrors medusalix/xone structure)
+# ==============================================================================
+
+# USB transport (IOKit / IOUSBFamily)
+add_library(xone_usb STATIC
+    "src/usb/usb_transport.cpp"
+)
+target_include_directories(xone_usb PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_usb PRIVATE cxx_std_23)
+target_compile_options(xone_usb PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_usb PRIVATE ${BASE_DEFINITIONS})
+
+# Auth + crypto (AES-CCMP key setup, ECDH, RSA — port from auth/)
+add_library(xone_auth STATIC
+    "src/auth/crypto.cpp"
+)
+target_include_directories(xone_auth PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_auth PRIVATE cxx_std_23)
+target_compile_options(xone_auth PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_auth PRIVATE ${BASE_DEFINITIONS})
+
+# MT76 chip protocol (firmware load, EFUSE, radio init, beacons)
+add_library(xone_mt76 STATIC
+    "src/mt76/mt76.cpp"
+)
+target_include_directories(xone_mt76 PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_mt76 PRIVATE cxx_std_23)
+target_compile_options(xone_mt76 PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_mt76 PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(xone_mt76 PUBLIC xone_usb)
+
+# GIP protocol (client lifecycle, handshake, status reports)
+add_library(xone_gip STATIC
+    "src/gip/protocol.cpp"
+)
+target_include_directories(xone_gip PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_gip PRIVATE cxx_std_23)
+target_compile_options(xone_gip PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_gip PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(xone_gip PUBLIC xone_auth xone_mt76)
+
+# Virtual HID gamepad presentation
+add_library(xone_hid STATIC
+    "src/hid/hid_device.cpp"
+)
+target_include_directories(xone_hid PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_hid PRIVATE cxx_std_23)
+target_compile_options(xone_hid PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_hid PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(xone_hid PUBLIC xone_gip)
+
+# C ABI bridge consumed by the Swift app and the test suite
+add_library(xone_api STATIC
+    "src/app/api.cpp"
+)
+target_include_directories(xone_api PUBLIC "${CMAKE_SOURCE_DIR}/include")
+target_compile_features(xone_api PRIVATE cxx_std_23)
+target_compile_options(xone_api PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(xone_api PRIVATE XONE_VERSION="${PROJECT_VERSION}")
+target_link_libraries(xone_api PUBLIC xone_hid)
+
+# ==============================================================================
+# macOS app (Swift entry point)
+# ==============================================================================
+add_executable(xone_app
+    "src/app/main.swift"
+)
+target_include_directories(xone_app PRIVATE "${CMAKE_SOURCE_DIR}/include")
+target_compile_definitions(xone_app PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(xone_app PRIVATE xone_api ${BASE_LIBRARIES})
+
+# Swift sees the C ABI via a bridging header (no module map required)
+target_compile_options(xone_app PRIVATE
+    -import-objc-header "${CMAKE_SOURCE_DIR}/include/app/xone_api.h"
+)
+
+# ==============================================================================
+# Tests
+# ==============================================================================
+option(BUILD_TESTING OFF "Build Unity test suites")
+if (BUILD_TESTING)
+    enable_testing()
+    find_package(Unity REQUIRED)
+    add_subdirectory(tests)
+endif()