A deadlocked main thread never crashes, so it leaves no crash report and no
artifact — incidence has been unmeasurable (n=1 confirmed, macOS 26.5.1,
FB24004458 / electron#52437). This forks a plain-Node watchdog sibling under
ELECTRON_RUN_AS_NODE that survives the deadlock, listens for a 2s heartbeat,
and after 45s of silence writes a marker to userData. The next launch consumes
it, records a durable crash breadcrumb, and emits a main_thread_hang_detected
telemetry event carrying unresponsive_ms and self_recovered.
Observes only — it never kills or relaunches the parent. A true positive
recovers nothing force-quitting wouldn't, while a false positive would SIGKILL
a live main thread mid-write. self_recovered counts exactly the stalls such a
killer would have gotten wrong, so recovery can be built on evidence if the
field numbers justify it.
macOS-only, packaged-only (ORCA_HANG_WATCHDOG_FORCE=1 to test), with sleep-gap
suppression and idempotent shutdown on will-quit.
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