On KeyboardInterrupt, brewpi.py cancels all asyncio tasks (letting
HeaterTask's `with device.open()` finally block run), then calls
heater.close() as belt-and-suspenders before closing the event loop.
On shutdown HeaterHendi.activate(False) now sets the switch to 0 instead
of disabling remote control, so the Hendi stays in remote mode at 0 W
rather than dropping back to its local panel state. HendiCtrl.close()
does the same (setSwitch(0)) then closes the serial port.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>