gateway stop and restart previously called kill_gateway_processes() which
scans ps aux and kills ALL gateway processes across all profiles. Starting
a profile gateway would nuke the main one (and vice versa).
Now:
- hermes gateway stop → only kills the current profile's gateway (PID file)
- hermes -p work gateway stop → only kills the 'work' profile's gateway
- hermes gateway stop --all → kills every gateway process (old behavior)
- hermes gateway restart → profile-scoped for manual fallback path
- hermes update → discovers and restarts ALL profile gateways (systemctl
list-units hermes-gateway*) since the code update is shared
Added stop_profile_gateway() which uses the HERMES_HOME-scoped PID file
instead of global process scanning.