feat: port GIP protocol and auth stack

Port the GIP protocol and authentication layers from medusalix/xone
into the C++ stack:

- crypto: SHA-256/HMAC (CommonCrypto), RSA PKCS#1 (Security.framework),
  and a self-contained P-256 ECDH validated against OpenSSL vectors
- auth: v1 (RSA) and v2 (ECDH) handshake state machine
- gip: header/varint/chunk handling and packet dispatch, with the kernel
  device model replaced by transport + client_listener interfaces

Adds test_crypto, test_auth, and test_gip suites.

Co-Authored-By: deepseek (deepseek/deepseek-v4-pro-0813): ported crypto, auth, and GIP

tests/CMakeLists.txt

@@ -15,6 +15,27 @@ target_compile_features(test_types PRIVATE cxx_std_23)
 add_test(NAME test_types COMMAND test_types)
 list(APPEND TEST_TARGETS test_types)
 
+add_executable(test_crypto test_crypto.cpp)
+target_include_directories(test_crypto PRIVATE "${CMAKE_SOURCE_DIR}/include")
+target_link_libraries(test_crypto PRIVATE xone_auth Unity::Unity)
+target_compile_features(test_crypto PRIVATE cxx_std_23)
+add_test(NAME test_crypto COMMAND test_crypto)
+list(APPEND TEST_TARGETS test_crypto)
+
+add_executable(test_auth test_auth.cpp)
+target_include_directories(test_auth PRIVATE "${CMAKE_SOURCE_DIR}/include")
+target_link_libraries(test_auth PRIVATE xone_auth Unity::Unity)
+target_compile_features(test_auth PRIVATE cxx_std_23)
+add_test(NAME test_auth COMMAND test_auth)
+list(APPEND TEST_TARGETS test_auth)
+
+add_executable(test_gip test_gip.cpp)
+target_include_directories(test_gip PRIVATE "${CMAKE_SOURCE_DIR}/include")
+target_link_libraries(test_gip PRIVATE xone_gip Unity::Unity)
+target_compile_features(test_gip PRIVATE cxx_std_23)
+add_test(NAME test_gip COMMAND test_gip)
+list(APPEND TEST_TARGETS test_gip)
+
 add_custom_target(check
     COMMAND ${CMAKE_CTEST_COMMAND}
             --test-dir "${CMAKE_BINARY_DIR}"