Function kill_process_group_forcefully 

pub(crate) fn kill_process_group_forcefully(child: &Child)

SIGKILL an entire process group in one shot — the unix analogue of Windows’ TerminateJobObject. child must have been spawned with .process_group(0) (both spawn_host_unix and srv_spawner::spawn_srv do this) so its pgid equals its own pid; negating the pid targets the whole group instead of just the one process, reaping any descendants (e.g. CEF’s forked renderer/GPU subprocesses) the launcher never tracks individually. Used by the teardown backstop (SPEC_LAUNCHER_TEARDOWN_BACKSTOP_2026_07_11) as the hard backstop after kill_process_group_gracefully’s brief grace window — reserved for whatever a graceful SIGTERM didn’t reap (a wedged-or-dead srv, or shells its own stop_all() couldn’t finish in time). No-op if the child has already exited (its pid may have been reaped; a stale pid’s negated kill returns ESRCH, ignored).