DaemonHandle's shutdown_tx (oneshot) is replaced with a CancellationToken
shared between the daemon loop and the IPC server. The token is the
single source of truth for "should we shut down" — `DaemonHandle::shutdown`
cancels it, and an IPC `Stop` request also cancels it.
- daemon/state: store the CancellationToken on DaemonHandle and clone it
on Clone (so cached IPC handles can still trigger shutdown).
- daemon/ipc: IpcServer takes a daemon_shutdown token; `Stop` now cancels
it instead of returning Ok and doing nothing. Add IpcClient with
`request`, `status`, and `stop` methods so the CLI can drive a
backgrounded daemon over the Unix socket.
- daemon/lifecycle: thread the token through run_daemon_loop and
run_session, pass a clone to IpcServer::new.
- lib.rs: re-export IpcClient/IpcCommand/IpcResponse so callers don't
have to reach into the daemon module.
- src/vpn_cmds.rs: `sunbeam disconnect` now actually talks to the daemon
via IpcClient::stop, and `sunbeam vpn status` queries IpcClient::status
and prints addresses + peer count + DERP home.
Adds the foreground VPN client commands. The daemon runs in-process
inside the CLI for the lifetime of `sunbeam connect` — no separate
background daemon yet, that can come later if needed.
- Cargo.toml: add sunbeam-net as a workspace dep, plus hostname/whoami
for building a per-machine netmap label like "sienna@laptop"
- src/config.rs: new `vpn-url` and `vpn-auth-key` fields on Context
- src/cli.rs: `Connect`, `Disconnect`, and `Vpn { Status }` verbs
- src/vpn_cmds.rs: command handlers
- cmd_connect reads VPN config from the active context, starts the
daemon at ~/.sunbeam/vpn, polls for Running, then blocks on ^C
before calling DaemonHandle::shutdown
- cmd_disconnect / cmd_vpn_status are placeholders that report based
on the control socket; actually talking to a backgrounded daemon
needs an IPC client (not yet exposed from sunbeam-net)
- src/workflows/mod.rs: `..Default::default()` on Context literals so
the new fields don't break the existing tests
