Replace the 'Power Off' / 73 message on colour displays with a shut-off
animation that collapses the current screen towards the middle (vertical
squeeze to a line, then horizontal collapse to a centre dot) like an old CRT.
Snapshots the live framebuffer into the (idle) notification offscreen buffer
so no extra RAM is needed; runs blocking with vTaskDelay between frames.
Mono displays keep the existing message. Docs updated.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
