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/TransformerPanel.h

@@ -0,0 +1,26 @@
+#pragma once
+#include <JuceHeader.h>
+#include "LookAndFeel.h"
+
+class TransformerPanel : public juce::Component
+{
+public:
+    TransformerPanel();
+    void resized() override;
+    void paint (juce::Graphics& g) override;
+
+    int getSelectedType() const { return currentType; }
+    void setSelectedType (int type);
+
+    juce::TextButton nickelButton  { "NICKEL" };
+    juce::TextButton ironButton    { "IRON" };
+    juce::TextButton steelButton   { "STEEL" };
+
+private:
+    juce::Label titleLabel;
+    int currentType = 0;  // 0=Off
+
+    void updateButtonStates();
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (TransformerPanel)
+};