Arduino CLI build system with HAL-based test architecture

Build and upload tool (arduino-build.sh):
- Compile, upload, and monitor via arduino-cli
- Device discovery with USB ID identification (--devices)
- Persistent reconnecting serial monitor (--watch)
- Split compile/upload workflow (--verify, --upload-only)
- First-time setup wizard (--setup)
- Comprehensive --help with troubleshooting and RedBoard specs

Testable application architecture:
- Hardware abstraction layer (lib/hal/) decouples logic from Arduino API
- Google Mock HAL for unit tests (exact call verification)
- Simulated HAL for system tests (GPIO state, virtual clock, I2C devices)
- Example I2C temperature sensor simulator (TMP102)
- Host-side test suite via CMake + Google Test (21 tests)

Example sketch:
- blink/ -- LED blink with button-controlled speed, wired through HAL

test/CMakeLists.txt

@@ -0,0 +1,70 @@
+cmake_minimum_required(VERSION 3.14)
+project(sparkfun_tests LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# --------------------------------------------------------------------------
+# Google Test (fetched automatically)
+# --------------------------------------------------------------------------
+include(FetchContent)
+FetchContent_Declare(
+    googletest
+    GIT_REPOSITORY https://github.com/google/googletest.git
+    GIT_TAG        v1.14.0
+)
+# Prevent gtest from overriding compiler/linker options on Windows
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+FetchContent_MakeAvailable(googletest)
+
+enable_testing()
+
+# --------------------------------------------------------------------------
+# Include paths -- same headers used by Arduino, but compiled on host
+# --------------------------------------------------------------------------
+set(LIB_DIR ${CMAKE_SOURCE_DIR}/../lib)
+
+include_directories(
+    ${LIB_DIR}/hal          # hal.h
+    ${LIB_DIR}/app          # blink_app.h
+    ${CMAKE_SOURCE_DIR}/mocks  # mock_hal.h, sim_hal.h
+)
+
+# --------------------------------------------------------------------------
+# Unit tests (Google Mock)
+# --------------------------------------------------------------------------
+add_executable(test_blink_unit
+    test_blink_unit.cpp
+)
+target_link_libraries(test_blink_unit
+    GTest::gtest_main
+    GTest::gmock
+)
+
+# --------------------------------------------------------------------------
+# System tests (SimHal)
+# --------------------------------------------------------------------------
+add_executable(test_blink_system
+    test_blink_system.cpp
+)
+target_link_libraries(test_blink_system
+    GTest::gtest_main
+)
+
+# --------------------------------------------------------------------------
+# I2C example tests
+# --------------------------------------------------------------------------
+add_executable(test_i2c_example
+    test_i2c_example.cpp
+)
+target_link_libraries(test_i2c_example
+    GTest::gtest_main
+)
+
+# --------------------------------------------------------------------------
+# Register with CTest
+# --------------------------------------------------------------------------
+include(GoogleTest)
+gtest_discover_tests(test_blink_unit)
+gtest_discover_tests(test_blink_system)
+gtest_discover_tests(test_i2c_example)