v183
Base: stable v181.

Single isolated compromise:
- delayed B shimmer frame: 125ms -> 120ms
- full frame metro remains 250ms

Reason:
v182 at 100ms improved menu entry but made the star shimmer visibly uneven.
120ms stays very close to v181's smooth 125/125 rhythm while retaining a
small extra handoff margin.

Everything else is exactly v181:
- Sustain behavior
- Stars routing
- OLED exit gate/cancel
- audio/AUX/LED
