The re-exec'd venv child spawned by
_reexec_dependency_sync_off_windows_shim completes every update step —
the receipt records success / "completed at command boundary" — but then
hangs in interpreter shutdown on a leftover non-daemon thread, freezing
the PowerShell window for minutes after "Update complete!". On the
hand-off path only (HERMES_UPDATE_REEXEC=1), after the receipt is
finalized, the update lock released, and stdio restored, flush and
os._exit(code) instead of unwinding — the same treatment #79040's cron
workaround applies. SystemExit codes (including early refusals)
propagate to the hard exit; real exceptions keep the normal raise path
so tracebacks still print. Non-hand-off invocations are untouched: the
marker env is set solely when the shim spawns the child.
Fixes#93581
liuhao1024