After the package-manager handoff, hermes update finishes on the bare store
interpreter and spawns the detached restart watcher as sys.executable -c.
The watcher imported gateway.status (utils -> hermes_yaml -> ruamel) and
hermes_cli.config, died with ModuleNotFoundError before relaunching, and
left every manually started gateway down after the update (gated on #124649).
Move the stdlib liveness probe (zombie-aware POSIX kill(0), Windows
OpenProcess) into hermes_cli._subprocess_compat, have gateway.status's
fallback delegate to it, and import only stdlib-backed modules in the
watcher.
Fixes#124649.
029445545c