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).
Builds on the salvaged force-exit fix:
- Route the start_gateway() SystemExit paths (clean-fatal-config #51228,
planned-restart, service-restart) through the same os._exit backstop. Those
paths previously fell through to normal interpreter finalization, leaving
them vulnerable to the SAME wedged-non-daemon-thread hang the boolean-return
paths now avoid. main() catches SystemExit and converts its code (None->0,
int->code, str->1) to os._exit. Every exit path is now wedge-proof.
- Document in the helper why bypassing atexit is safe (remove_pid_file +
release_gateway_runtime_lock are performed explicitly in start_gateway
teardown) and why logging is not flushed (synchronous RotatingFileHandlers).
- Tests: assert termination via os._exit not SystemExit (adapted from
@AgenticSpark's PR #53122, a duplicate of #53121), plus SystemExit(78) is
routed through os._exit(78) and SystemExit(None) maps to os._exit(0).
