Multi-output routing (7 stereo buses) + VU meter fix

- 7 stereo output buses: Main, Kick, Snare, HiHat, Toms, Cymbals, Perc
- Each pad pre-assigned to appropriate bus (configurable via outputBus)
- Pads route to assigned bus if active, fallback to Main if not
- Master FX (limiter) applied to Main bus only
- isBusesLayoutSupported: Main must be stereo, aux can be stereo or disabled
- All buses enabled by default for REAPER multi-output detection
- VU meter: switched from RMS to peak measurement (getMagnitude)
- VU meter: sqrt scaling for better visibility on transient material
- VU meter: removed distracting dB scale markers
- VU meter: fast attack / medium release smoothing
- README updated with multi-output routing section

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -28,10 +28,16 @@ Free, open-source VST3 drum sampler plugin built with JUCE.
 - Reverb (Size, Decay)
 - Each FX toggleable with animated switches
 
+### Multi-Output Routing
+- 7 stereo output buses: Main, Kick, Snare, HiHat, Toms, Cymbals, Perc
+- Each pad pre-assigned to its bus (configurable)
+- In REAPER: enable additional outputs via routing for separate track processing
+- Pads with inactive buses automatically fall back to Main
+
 ### Master Bus
 - Master Volume, Tune, Pan
 - Output Limiter (0dB brickwall, toggleable)
-- VU meter with peak hold
+- Peak VU meter with hold indicator
 
 ### GUI
 - Dark modern UI inspired by hardware drum machines