v191 latch-off key-star flash update
- Base: KEYSTARS + FRAME_BUDGET + VIBRATO_FIX
- Key stars now trigger on note-on regardless of latch state.
- Latch OFF: each triggered slot stays active for 120 ms.
- Latch ON: each triggered slot stays active for 4800 ms.
- No key-triggered OLED redraw/flip was added; stars remain rendered only by the normal visual frame cycle.
