internal/cli reimplements cli/src: start/stop/restart/status with the
awg-ctrl health gate, credentials, join/unjoin, peers [drop], monitor
install/status/remove and the interactive menu. Same cli.env, pid files,
logs and messages. Without arguments or with an operator command the binary
acts as the CLI; ctrl/ui/agent stay service roles.
- services are started as the same binary (`awg-control ctrl|ui|agent`),
detached into their own session, from the same working directories
- processes started by the Node CLI (tsx … index.ts / server.ts) are still
recognised, so `stop` and `status` work across the switch
- after join the fresh restart gets the original environment, so a rejoin
picks up the new cli.env instead of the inherited old CORE_* values
- install root: AWG_ROOT, else the nearest parent of the binary with cli/ or
.env, else /opt/awg-control
Checked end to end on stubbed awg: start/status/stop, credentials, join to
the panel's own hub (with and without --no-panel), peers listing and drop,
unjoin, menu.
