pyserial and spidev are Linux/Pi-only (spidev requires the kernel SPI
driver and won't install on macOS/Windows). Dev machines use
requirements.txt; the Pi uses requirements-hw.txt which pulls in the
base file via -r.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SH2D4LRuCnhLSzoYerAfJX
