Initial release — InstaGrain granular synthesizer v1.0

8-voice polyphonic granular synth (VST3/AU/LV2) with:
- 128 grain pool per voice, Hann windowing, linear interpolation
- Root note selector, sample rate correction, sustain pedal (CC64)
- Scatter controls, direction modes (Fwd/Rev/PingPong), freeze
- ADSR envelope, global filter (LP/HP/BP), reverb
- Waveform display with grain visualization
- Drag & drop sample loading, full state save/restore
- CI/CD for Windows/macOS/Linux

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

Source/Grain.h

@@ -0,0 +1,45 @@
+#pragma once
+#include <JuceHeader.h>
+
+// ============================================================
+// Hann window lookup table (1024 points, computed once)
+// ============================================================
+struct GrainWindow
+{
+    static constexpr int tableSize = 1024;
+    float table[tableSize];
+
+    GrainWindow()
+    {
+        for (int i = 0; i < tableSize; ++i)
+        {
+            float phase = (float) i / (float) (tableSize - 1);
+            table[i] = 0.5f * (1.0f - std::cos (juce::MathConstants<float>::twoPi * phase));
+        }
+    }
+
+    float getValue (float phase) const
+    {
+        float index = juce::jlimit (0.0f, 1.0f, phase) * (float) (tableSize - 1);
+        int i0 = (int) index;
+        int i1 = std::min (i0 + 1, tableSize - 1);
+        float frac = index - (float) i0;
+        return table[i0] + frac * (table[i1] - table[i0]);
+    }
+};
+
+// ============================================================
+// Single grain
+// ============================================================
+struct Grain
+{
+    int startSample = 0;            // where in source buffer
+    int lengthSamples = 0;          // grain duration in samples
+    float pitchRatio = 1.0f;        // playback speed
+    double readPosition = 0.0;      // current fractional read position
+    int samplesElapsed = 0;         // output samples generated
+    float panPosition = 0.0f;       // -1 left, +1 right
+    float volume = 1.0f;
+    bool reverse = false;
+    bool active = false;
+};