Extracted from beff5dd5 on archy-hwconfig (the rest of that commit is
flash-feature code staying on its branch): a device that connects then
drops within seconds — e.g. mid-boot-loop — kept resetting backoff to
5s forever, and every retry's open() toggles DTR/RTS which itself
resets ESP32-family boards. Backoff now only resets after a session
survives STABLE_SESSION_THRESHOLD (20s), so an unstable device gets
progressively longer quiet gaps to actually finish booting.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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