- platform gate accepts Darwin and Linux; other platforms are refused
- default install root follows each platform's convention
(~/Library/Application Support vs ~/.local/share)
- LAN IP discovery uses ip -4/hostname -I on Linux, ipconfig on macOS
- port occupancy checks fall back from lsof to ss
- API process gets MULTI_SIMADMIN_SECRET_BACKEND pinned per platform
- README documents the per-platform secret storage
chick