dsp/: add spectral detector with envelope + peak suppression

- Detector computes smoothed spectral envelope
- Finds peaks exceeding envelope
- Creates per-bin suppression mask
- Applies mask in frequency domain before ISTFT
- Default params: sharpness=1.0, selectivity=0.5, depth=0.3

Verified: burst500.wav → output RMS reduced from 0.0678 to 0.0476

dsp/spectral.hpp

@@ -4,6 +4,7 @@
 #include <complex>
 #include <vector>
 #include "fft.hpp"
+#include "detect.hpp"
 
 constexpr size_t DEFAULT_NFFT = 2048;
 constexpr size_t DEFAULT_HOP = 512;
@@ -12,9 +13,10 @@ class SpectralProcessor {
 public:
     SpectralProcessor(size_t nfft = DEFAULT_NFFT, size_t hop = DEFAULT_HOP);
     ~SpectralProcessor();
-    
+
+    void setDetectorParams(float sharpness, float selectivity, float depth);
     void processBlock(float* in, float* out, size_t num_samples, size_t num_channels = 1);
-    
+
 private:
     size_t nfft_;
     size_t hop_;
@@ -23,12 +25,12 @@ private:
     std::complex<double>* buf_;
     std::complex<double>* tmp_buf_;
     std::vector<float> overlap_;
+    std::vector<float> mask_;
+    Detector detector_;
     size_t frame_count_;
     size_t output_pos_;
-    
+
     void computeWindow();
     void stftFrame(const float* in, std::complex<double>* out);
     void istftFrame(std::complex<double>* in, float* out, float* overlap);
-    void updateDetector();
 };
-