Spins up Headscale 0.23 (with embedded DERP) plus two Tailscale peers
in docker compose, generates pre-auth keys, and runs three integration
tests behind the `integration` feature:
- test_register_and_receive_netmap: full TS2021 → register → first
netmap fetch
- test_proxy_listener_accepts: starts the daemon and waits for it to
reach the Running state
- test_daemon_lifecycle: full lifecycle including DERP connect, then
clean shutdown via the DaemonHandle
Run with `sunbeam-net/tests/run.sh` (handles compose up/down + auth
key provisioning) or manually via cargo nextest with the env vars
SUNBEAM_NET_TEST_AUTH_KEY and SUNBEAM_NET_TEST_COORD_URL set.