Closes the survivors StrykerJS reported over the new supervisor code (61 mutants, 41 killed, 20 survived): the pid
file is removed when its worker exits and not when it spawned nothing, the restart kill is SIGKILL (a stubborn stray
and a SIGTERM-proof encoder child), the group match is the pid file's, not any marked process. killGroup loses its
unused return value.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>