Show a small lightning-bolt icon to the left of the battery indicator on
the ui-new home screen while the device is externally powered, and a plug
icon once the battery reads full. The bolt/plug sits beside the battery so
the fill bar stays clean and uninterrupted. When a buzzer is present, the
mute icon shifts one slot further left so the two never overlap.
Charging state is derived from board.isExternalPowered(), so this works on
any board that reports external power (e.g. the nRF52 VBUS-detect path).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
