The apply handler sent SIGTERM then fired a 150 ms setTimeout to reload
the renderer. If the backend took longer to shut down the port was still
bound when startHermes() ran after reload, causing an "address already
in use" failure.
Capture the process reference before resetHermesConnection() nulls it,
then await the actual exit event. A 5 s SIGKILL fallback ensures the
wait never hangs if the backend ignores SIGTERM.
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