The low-battery blink would stay frozen mid-cycle (or briefly resume
during reconnect retries) after a controller died and lost connection,
because the stale-report check stopped toggling but never turned the
LED off, and the cached interrupt_in_data[52] still read low.
New `battery_led_on_disconnect()` clears blink state, forces the LED
off, and zeros last_report_us so the stale-check early-return blocks
any new blink until a fresh 0x31 report arrives on the next connection.
Called from bt.cpp's HCI_EVENT_DISCONNECTION_COMPLETE handler.
Stale-check in the tick also now forces LED off when it fires while a
blink was in progress (defense in depth for unclean disconnects).
Same bug exists in upstream awalol/DS5Dongle (their battery_led.cpp is
byte-identical to ours pre-fix) — Sura Academy reported it in their
Discord. Plan to send this back as a PR after we validate it locally.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
