Sandboxed commands previously ran as `sudo -u _greywall`, breaking user
identity (home dir, SSH keys, git config). Now uses `sudo -u #<uid> -g
_greywall` so the process keeps the real user's identity while pf
matches
on EGID for traffic routing.
Key changes:
- pf rules use `group <GID>` instead of `user _greywall`
- GID resolved dynamically at daemon startup (not hardcoded, since macOS
system groups like com.apple.access_ssh may claim preferred IDs)
- Sudoers rule installed at /etc/sudoers.d/greywall (validated with
visudo)
- Invoking user added to _greywall group via dscl (not dseditgroup,
which
clobbers group attributes)
- tun2socks device discovery scans both stdout and stderr (fixes 10s
timeout caused by STACK message going to stdout)
- Always-on daemon logging for session create/destroy events
