A working document in the house style (phases, gates): two small circles
in the lower-right corner of the screen, one per Disk II drive — red when
the drive is active, grey when idle, hidden entirely when the motor is
off. Rendered as an SDL-side overlay texture driven by the existing
Dsk::motor_lit / active_drive signals, so the pure screen renderer and
the golden BMPs stay untouched.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012KgAw4A42H9mgKGWABTJoj