Reduce plugin width by 102px and fix bottom panel layout to scale proportionally

Source/PluginProcessor.h

@@ -43,6 +43,11 @@ public:
     void psolaStretch(int targetLength);
     float getHostBpm() const;
 
+    void undo();
+    void redo();
+    bool canUndo() const;
+    bool canRedo() const;
+
     juce::AudioProcessorValueTreeState& getAPVTS() { return apvts; }
     SliceManager& getSliceManager() { return sliceManager; }
 
@@ -56,6 +61,8 @@ public:
     std::atomic<int> currentPlaybackSample { -1 };
     std::atomic<int> currentActiveSlice { -1 };
     std::atomic<int> selectedSlice { -1 };
+    std::atomic<float> outputLevelL { 0.0f };
+    std::atomic<float> outputLevelR { 0.0f };
 
 private:
     juce::AudioProcessorValueTreeState apvts;
@@ -73,6 +80,17 @@ private:
     int currentFileIndex = -1;
     void refreshFolderList();
 
+    struct UndoState
+    {
+        juce::File file;
+        std::vector<SliceManager::Slice> slices;
+    };
+    std::vector<UndoState> undoStack;
+    std::vector<UndoState> redoStack;
+    static constexpr int maxUndoDepth = 10;
+    void pushUndoState();
+    bool restoringFromUndo = false;
+
     enum class AmpStage { Idle, Attack, Decay, Sustain, Release };
     enum class FilterType { LP12, LP24, HP, BP, Notch };