Initial release — InstaShadow mastering compressor v1.0

Dual-stage compressor (optical + VCA) with output transformer saturation.
- Port-Hamiltonian T4B opto-cell model with implicit trapezoidal integration
- Feed-forward VCA with 7 ratios, 6 attack/release presets, Dual release mode
- 3 transformer types (Nickel/Iron/Steel) with 4x oversampled waveshaping
- Analog-style needle VU meters, horizontal GR meters
- Sidechain HPF, stereo link, independent section bypass
- Full state save/restore, CI/CD for Windows/macOS/Linux

Source/PluginProcessor.h

@@ -0,0 +1,41 @@
+#pragma once
+#include <JuceHeader.h>
+#include "CompressorEngine.h"
+
+class InstaShadowProcessor : public juce::AudioProcessor
+{
+public:
+    InstaShadowProcessor();
+    ~InstaShadowProcessor() override;
+
+    void prepareToPlay (double sampleRate, int samplesPerBlock) override;
+    void releaseResources() override;
+
+    bool isBusesLayoutSupported (const BusesLayout& layouts) const override;
+    void processBlock (juce::AudioBuffer<float>&, juce::MidiBuffer&) override;
+
+    juce::AudioProcessorEditor* createEditor() override;
+    bool hasEditor() const override { return true; }
+
+    const juce::String getName() const override { return JucePlugin_Name; }
+    bool acceptsMidi() const override { return false; }
+    bool producesMidi() const override { return false; }
+    bool isMidiEffect() const override { return false; }
+    double getTailLengthSeconds() const override { return 0.0; }
+
+    int getNumPrograms() override { return 1; }
+    int getCurrentProgram() override { return 0; }
+    void setCurrentProgram (int) override {}
+    const juce::String getProgramName (int) override { return {}; }
+    void changeProgramName (int, const juce::String&) override {}
+
+    void getStateInformation (juce::MemoryBlock& destData) override;
+    void setStateInformation (const void* data, int sizeInBytes) override;
+
+    CompressorEngine& getEngine() { return engine; }
+
+private:
+    CompressorEngine engine;
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (InstaShadowProcessor)
+};