feat(freebsd): full FreeBSD 15.0 compatibility

- board: detect cuaU* serial ports in fallback scanner, filter .init/.lock nodes
- board: fall through to OS scan when arduino-cli returns empty (serial-discovery
  uses unsupported Linux syscalls on FreeBSD)
- board: recognize cuaU* port names as USB in is_usb()
- upload.sh: fix silent exit under set -euo pipefail when vid_pid grep finds
  nothing (|| true on LOCAL_PORT and LOCAL_VID_PID greps)
- upload.sh: add cuaU to auto-detect port pattern
- doctor: detect dialer and operator group membership, offer --fix for both
- doctor: detect avr-size installed but not on PATH, offer --fix to add to
  shell rc file via detect_shell_rc()
- doctor: context-aware hardware section (suppress misleading messages when
  groups not yet applied)
- doctor: FreeBSD-specific troubleshooting hints throughout
- devices: suppress arduino-cli board detection section on FreeBSD (broken
  due to serial-discovery syscall issues)
- devices: always show USB hub tip on FreeBSD
- devices: FreeBSD-specific troubleshooting checklist with sequential numbering
  on all platforms

templates/basic/test/run_tests.sh

@@ -17,6 +17,17 @@ set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 BUILD_DIR="$SCRIPT_DIR/build"
 
+# Portable CPU count -- BSD make requires a number after -j, GNU make does not
+cpu_count() {
+    if command -v nproc &>/dev/null; then
+        nproc
+    elif command -v sysctl &>/dev/null; then
+        sysctl -n hw.ncpu
+    else
+        echo 4
+    fi
+}
+
 # Color output
 if [[ -t 1 ]]; then
     RED=$'\033[0;31m'; GRN=$'\033[0;32m'; CYN=$'\033[0;36m'
@@ -40,7 +51,7 @@ for arg in "$@"; do
     esac
 done
 
-command -v cmake &>/dev/null || die "cmake not found. Install: sudo apt install cmake"
+command -v cmake &>/dev/null || die "cmake not found. Install: pkg install cmake (FreeBSD), apt install cmake (Debian/Ubuntu), dnf install cmake (Fedora)"
 command -v g++ &>/dev/null || command -v clang++ &>/dev/null || die "No C++ compiler found"
 command -v git &>/dev/null || die "git not found (needed to fetch Google Test)"
 
@@ -55,7 +66,7 @@ if [[ ! -f "$BUILD_DIR/CMakeCache.txt" ]]; then
 fi
 
 info "Building tests..."
-cmake --build "$BUILD_DIR" --parallel
+cmake --build "$BUILD_DIR" --parallel "$(cpu_count)"
 
 echo ""
 info "${BLD}Running tests...${RST}"