Initial commit: InstaLPEQ linear phase EQ plugin

Full-featured linear phase EQ with interactive graphical curve display.
FIR-based processing (8192-tap), 8 parametric bands, multi-platform
CI/CD (Windows/macOS/Linux), InstaDrums visual style.

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

Source/NodeParameterPanel.h

@@ -0,0 +1,49 @@
+#pragma once
+#include <JuceHeader.h>
+#include "EQBand.h"
+
+class NodeParameterPanel : public juce::Component,
+                           private juce::Slider::Listener,
+                           private juce::ComboBox::Listener,
+                           private juce::Button::Listener
+{
+public:
+    struct Listener
+    {
+        virtual ~Listener() = default;
+        virtual void nodeParameterChanged (int bandIndex, const EQBand& band) = 0;
+        virtual void nodeDeleteRequested (int bandIndex) = 0;
+    };
+
+    NodeParameterPanel();
+
+    void setListener (Listener* l) { listener = l; }
+    void setSelectedBand (int index, const EQBand* band);
+    int getSelectedIndex() const { return selectedIndex; }
+
+    void resized() override;
+    void paint (juce::Graphics& g) override;
+
+private:
+    void sliderValueChanged (juce::Slider* slider) override;
+    void comboBoxChanged (juce::ComboBox* box) override;
+    void buttonClicked (juce::Button* button) override;
+
+    int selectedIndex = -1;
+    EQBand currentBand;
+    bool updatingFromExternal = false;
+
+    juce::Slider freqSlider, gainSlider, qSlider;
+    juce::Label freqLabel { {}, "FREQ" };
+    juce::Label gainLabel { {}, "GAIN" };
+    juce::Label qLabel    { {}, "Q" };
+    juce::Label bandInfoLabel { {}, "No band selected" };
+    juce::ComboBox typeSelector;
+    juce::TextButton deleteButton { "DELETE" };
+
+    Listener* listener = nullptr;
+
+    void setupSlider (juce::Slider& s, juce::Label& l, double min, double max, double step, const char* suffix);
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NodeParameterPanel)
+};