Add mock Arduino for x86_64 host-side testing

Complete Arduino API mock (mock_arduino.h/cpp) enabling application
code to compile and run on PC without hardware. Includes MockSerial,
String class, GPIO/analog/timing/interrupt mocks with state tracking
and test control API.

- Arduino.h, Wire.h, SPI.h shims intercept includes in test builds
- System test template (test_system.cpp) using SimHal
- CMakeLists.txt builds mock_arduino as static lib, links both suites
- Root test.sh/test.bat with --unit/--system/--clean/--verbose flags
- test.bat auto-detects MSVC via vswhere + vcvarsall.bat
- Doctor reports nuanced compiler status (on PATH vs installed)
- Refresh pulls mock infrastructure into existing projects
- 15 tests passing: 7 unit (MockHal) + 8 system (SimHal)

templates/basic/test.sh

@@ -0,0 +1,124 @@
+#!/usr/bin/env bash
+#
+# test.sh -- Build and run all host-side tests (no Arduino board needed)
+#
+# Usage:
+#   ./test.sh              Build and run all tests
+#   ./test.sh --clean      Clean rebuild
+#   ./test.sh --verbose    Verbose test output
+#   ./test.sh --unit       Run only unit tests
+#   ./test.sh --system     Run only system tests
+#
+# This script builds your application against mock_arduino (a fake Arduino
+# environment) and runs Google Test suites. Your app code compiles and runs
+# on your PC -- no board, no wires, no USB.
+#
+# Prerequisites:
+#   cmake >= 3.14, a C++ compiler (g++, clang++, or MSVC), git
+#
+# First run downloads Google Test automatically (~30 seconds).
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TEST_DIR="$SCRIPT_DIR/test"
+BUILD_DIR="$TEST_DIR/build"
+
+# Color output
+if [[ -t 1 ]]; then
+    RED=$'\033[0;31m'; GRN=$'\033[0;32m'; CYN=$'\033[0;36m'
+    YLW=$'\033[0;33m'; BLD=$'\033[1m';    RST=$'\033[0m'
+else
+    RED=''; GRN=''; CYN=''; YLW=''; BLD=''; RST=''
+fi
+
+info() { echo -e "${CYN}[TEST]${RST}  $*"; }
+ok()   { echo -e "${GRN}[PASS]${RST}  $*"; }
+warn() { echo -e "${YLW}[WARN]${RST}  $*"; }
+die()  { echo -e "${RED}[FAIL]${RST}  $*" >&2; exit 1; }
+
+DO_CLEAN=0
+VERBOSE=""
+FILTER=""
+
+for arg in "$@"; do
+    case "$arg" in
+        --clean)   DO_CLEAN=1 ;;
+        --verbose) VERBOSE="--verbose" ;;
+        --unit)    FILTER="-R test_unit" ;;
+        --system)  FILTER="-R test_system" ;;
+        -h|--help)
+            echo "Usage: ./test.sh [--clean] [--verbose] [--unit|--system]"
+            echo ""
+            echo "  --clean      Delete build cache and rebuild from scratch"
+            echo "  --verbose    Show individual test names and output"
+            echo "  --unit       Run only unit tests (Google Mock)"
+            echo "  --system     Run only system tests (SimHal)"
+            exit 0
+            ;;
+        *)         die "Unknown option: $arg (try --help)" ;;
+    esac
+done
+
+# -- Check prerequisites ----------------------------------------------------
+
+if ! command -v cmake &>/dev/null; then
+    die "cmake not found."
+    echo "  Install:" >&2
+    if [[ "$(uname)" == "Darwin" ]]; then
+        echo "    brew install cmake" >&2
+    else
+        echo "    sudo apt install cmake   (Debian/Ubuntu)" >&2
+        echo "    sudo dnf install cmake   (Fedora)" >&2
+    fi
+    echo "" >&2
+    echo "  Or run: anvil doctor --fix" >&2
+    exit 1
+fi
+
+if ! command -v g++ &>/dev/null && ! command -v clang++ &>/dev/null; then
+    die "No C++ compiler found (need g++ or clang++)."
+    echo "  Or run: anvil doctor --fix" >&2
+    exit 1
+fi
+
+if ! command -v git &>/dev/null; then
+    die "git not found (needed to fetch Google Test)."
+    exit 1
+fi
+
+# -- Build -------------------------------------------------------------------
+
+if [[ $DO_CLEAN -eq 1 ]] && [[ -d "$BUILD_DIR" ]]; then
+    info "Cleaning build directory..."
+    rm -rf "$BUILD_DIR"
+fi
+
+if [[ ! -f "$BUILD_DIR/CMakeCache.txt" ]]; then
+    info "Configuring test build. First run will fetch Google Test..."
+    cmake -S "$TEST_DIR" -B "$BUILD_DIR" -DCMAKE_BUILD_TYPE=Debug 2>&1 | \
+        while IFS= read -r line; do echo "       $line"; done
+    echo ""
+fi
+
+info "Building tests..."
+cmake --build "$BUILD_DIR" --parallel 2>&1 | \
+    while IFS= read -r line; do echo "       $line"; done
+
+echo ""
+info "${BLD}Running tests...${RST}"
+echo ""
+
+# -- Run ---------------------------------------------------------------------
+
+CTEST_ARGS=("--test-dir" "$BUILD_DIR" "--output-on-failure")
+[[ -n "$VERBOSE" ]] && CTEST_ARGS+=("--verbose")
+[[ -n "$FILTER" ]] && CTEST_ARGS+=($FILTER)
+
+if ctest "${CTEST_ARGS[@]}"; then
+    echo ""
+    ok "${BLD}All tests passed.${RST}"
+else
+    echo ""
+    die "Some tests failed."
+fi