Follow-up to #54111. That PR routed the early SystemExit exit paths
(clean-fatal-config #51228, startup-aborted-before-running) through
_exit_after_graceful_shutdown / os._exit. Those paths raise right after
runner.start() without going through _stop_impl, so they relied on atexit
to release the PID file + runtime lock — and os._exit bypasses atexit,
leaking both.
Release them explicitly in the backstop (the single guaranteed cleanup
chokepoint). Both calls are idempotent: no-op on the normal _stop_impl
path, actual cleanup on the early-exit paths. Corrects the now-inaccurate
docstring claim that teardown always ran first. Adds a guard test plus the
missing str-code->1 coverage.
E2E: real PID file written + lock acquired, _exit_after_graceful_shutdown(78)
exits code 78 AND removes the PID file (leak confirmed closed).
kshitijk4poor
df27267ed7