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>

Source/PluginProcessor.h

@@ -21,8 +21,13 @@ public:
     const juce::String getName() const override { return JucePlugin_Name; }
     bool acceptsMidi() const override { return true; }
     bool producesMidi() const override { return true; }
+    bool isBusesLayoutSupported (const BusesLayout& layouts) const override;
     double getTailLengthSeconds() const override { return 0.0; }
 
+    // Output bus names
+    static constexpr int numOutputBuses = 7;
+    static const char* const outputBusNames[numOutputBuses];
+
     int getNumPrograms() override { return 1; }
     int getCurrentProgram() override { return 0; }
     void setCurrentProgram (int) override {}