P4: port framed_render.py model to C++ (FramedDetector: twin-res -> level -> Pchip LUT -> warp -> res^rp gain), replace empirical Detector; tt_base 49.93%->61.45% (single-band); multi-band refs still 100% (model is single-band)

dsp/framed_model.hpp

@@ -0,0 +1,36 @@
+#pragma once
+#include <cstddef>
+#include <complex>
+#include <vector>
+
+// FramedDetector — C++ port of framed_render.py (Phase 5 pilot, mean=0.175 dB).
+// Per-frame per-bin mask:
+//   res[f] = |2B(z)/A(z)|        (twin resonance, detkernel::twin)
+//   am     = 2|X_k|/wsum         (per-bin input amplitude, smoothed attack/release)
+//   xv     = log10(am / res)
+//   C      = G_FIT*LUT(xv) + W_FIT*warp(f)^A_FIT
+//   gain   = max(1-C, eps) * res^(rp0*Q^drp)
+class FramedDetector {
+public:
+    FramedDetector(size_t nfft, float sample_rate);
+    ~FramedDetector();
+
+    // fc = band center freq, q = resonance Q (>=1). Precomputes res[] + warp[].
+    void setParams(float fc, float q);
+
+    // spectrum = forward FFT of one windowed frame (nfft/2+1 bins used).
+    // mask output = per-bin complex gain (nfft entries, mirror applied).
+    void processFrame(const std::complex<double>* spectrum, float* mask);
+
+private:
+    size_t nfft_;
+    float sample_rate_;
+    float fc_;
+    float q_;
+    double wsum_;
+
+    std::vector<float> res_;      // per-bin |2B/A|
+    std::vector<float> warp_;     // per-bin warp tilt
+    std::vector<float> am_;       // smoothed per-bin amplitude state
+    bool inited_;
+};