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.cpp

@@ -0,0 +1,84 @@
+#include "TransformerPanel.h"
+
+TransformerPanel::TransformerPanel()
+{
+    titleLabel.setText ("TRANSFORMER", juce::dontSendNotification);
+    titleLabel.setJustificationType (juce::Justification::centredLeft);
+    titleLabel.setColour (juce::Label::textColourId, InstaShadowLookAndFeel::textPrimary);
+    addAndMakeVisible (titleLabel);
+
+    auto setupButton = [this] (juce::TextButton& btn, int typeId)
+    {
+        btn.setClickingTogglesState (false);
+        btn.onClick = [this, typeId, &btn]
+        {
+            if (currentType == typeId)
+                currentType = 0;  // deselect → Off
+            else
+                currentType = typeId;
+            updateButtonStates();
+        };
+        addAndMakeVisible (btn);
+    };
+
+    setupButton (nickelButton, 1);
+    setupButton (ironButton, 2);
+    setupButton (steelButton, 3);
+
+    updateButtonStates();
+}
+
+void TransformerPanel::setSelectedType (int type)
+{
+    currentType = std::clamp (type, 0, 3);
+    updateButtonStates();
+}
+
+void TransformerPanel::updateButtonStates()
+{
+    auto setColour = [this] (juce::TextButton& btn, bool active)
+    {
+        if (active)
+        {
+            btn.setColour (juce::TextButton::buttonColourId, InstaShadowLookAndFeel::accent.withAlpha (0.4f));
+            btn.setColour (juce::TextButton::textColourOffId, InstaShadowLookAndFeel::accent);
+        }
+        else
+        {
+            btn.setColour (juce::TextButton::buttonColourId, InstaShadowLookAndFeel::bgMedium);
+            btn.setColour (juce::TextButton::textColourOffId, InstaShadowLookAndFeel::textSecondary);
+        }
+    };
+
+    setColour (nickelButton, currentType == 1);
+    setColour (ironButton, currentType == 2);
+    setColour (steelButton, currentType == 3);
+
+    repaint();
+}
+
+void TransformerPanel::resized()
+{
+    auto bounds = getLocalBounds().reduced (4);
+    titleLabel.setBounds (bounds.removeFromTop (20));
+
+    auto btnArea = bounds.reduced (8, 4);
+    int btnH = std::min ((btnArea.getHeight() - 8) / 3, 28);
+    int totalH = btnH * 3 + 8;
+    auto centred = btnArea.withSizeKeepingCentre (std::min (btnArea.getWidth(), 120), totalH);
+
+    nickelButton.setBounds (centred.removeFromTop (btnH).reduced (0, 1));
+    centred.removeFromTop (4);
+    ironButton.setBounds (centred.removeFromTop (btnH).reduced (0, 1));
+    centred.removeFromTop (4);
+    steelButton.setBounds (centred.removeFromTop (btnH).reduced (0, 1));
+}
+
+void TransformerPanel::paint (juce::Graphics& g)
+{
+    auto bounds = getLocalBounds().toFloat();
+    g.setColour (InstaShadowLookAndFeel::bgMedium.withAlpha (0.5f));
+    g.fillRoundedRectangle (bounds, 4.0f);
+    g.setColour (InstaShadowLookAndFeel::bgLight.withAlpha (0.3f));
+    g.drawRoundedRectangle (bounds, 4.0f, 1.0f);
+}