spectral: vectors instead of new[]; vlaw: extract law + vlaw_check target

- spectral.cpp: window_/buf_/tmp_buf_/fir_buf_/fir_freq_ as std::vector (no
  exception-leak in ctor, destructor = default)
- framed_model.hpp: extract vlaw_cut/vlaw_mask inline (BLOCKMAP:314 softplus)
- dsp/vlaw_check.cpp: unit test for law (monotonic, zero-level, delta, ref,
  comb-neutral) — PASS
- CMake: add vlaw_check target
- Guard: corpus --compare d=+0.000, fn529fe0_check PASS, twin_check PASS

dsp/spectral.cpp

@@ -12,13 +12,13 @@
 SpectralProcessor::SpectralProcessor(size_t nfft, size_t hop, float sample_rate)
     : nfft_(nfft), hop_(hop), frame_count_(0), output_pos_(0),
       detector_(nfft, sample_rate) {
-    window_ = new double[nfft_];
+    window_.resize(nfft_);
     computeWindow();
     fft::init_plan(&plan_, static_cast<uint32_t>(std::log2(nfft_)));
-    buf_ = new std::complex<double>[nfft_];
-    tmp_buf_ = new std::complex<double>[nfft_];
-    fir_buf_ = new std::complex<double>[nfft_];
-    fir_freq_ = new std::complex<double>[nfft_];
+    buf_.resize(nfft_);
+    tmp_buf_.resize(nfft_);
+    fir_buf_.resize(nfft_);
+    fir_freq_.resize(nfft_);
     overlap_.resize(nfft_, 0.0f);
     mask_.resize(nfft_, 1.0f);
 
@@ -30,13 +30,7 @@ SpectralProcessor::SpectralProcessor(size_t nfft, size_t hop, float sample_rate)
     }
 }
 
-SpectralProcessor::~SpectralProcessor() {
-    delete[] window_;
-    delete[] buf_;
-    delete[] tmp_buf_;
-    delete[] fir_buf_;
-    delete[] fir_freq_;
-}
+SpectralProcessor::~SpectralProcessor() = default;
 
 void SpectralProcessor::setDetectorParams(const std::vector<DetectorBand>& bands) {
     detector_.setParams(bands);
@@ -63,8 +57,8 @@ void SpectralProcessor::stftFrame(const float* in, std::complex<double>* out) {
 }
 
 void SpectralProcessor::istftFrame(std::complex<double>* in, float* out, float* overlap) {
-    memcpy(tmp_buf_, in, nfft_ * sizeof(std::complex<double>));
-    fft::execute_inverse(&plan_, tmp_buf_);
+    memcpy(tmp_buf_.data(), in, nfft_ * sizeof(std::complex<double>));
+    fft::execute_inverse(&plan_, tmp_buf_.data());
     static bool wola_computed = false;
     static float wola_norm = 1.0f;
     // RT_SYN: 0=synthesis window = analysis window (WOLA), 1=none
@@ -279,9 +273,9 @@ void SpectralProcessor::processBlock(float* in, float* out, size_t num_samples,
     for (size_t f = 0; f < nframes; f++) {
         size_t offset = f * hop_;
         if (offset + nfft_ > num_samples) break;
-        stftFrame(in + offset, buf_);
+        stftFrame(in + offset, buf_.data());
 
-        detector_.processFrame(buf_, mask_.data());
+        detector_.processFrame(buf_.data(), mask_.data());
 
         if (firconv == 3) {
             // RT_FIRCONV=3 (NOTES 24k): plugin application law decoded live:
@@ -296,7 +290,7 @@ void SpectralProcessor::processBlock(float* in, float* out, size_t num_samples,
             // RT_FIRCONV=2: Full FIR construction pipeline (52b550-52b8bb).
             // mask → reciprocal (1/mask) → window → normalize → complex multiply.
             // This replicates the plugin's FFT-conv FIR design path.
-            buildFirFromMask(mask_.data(), fir_freq_, nfft_);
+            buildFirFromMask(mask_.data(), fir_freq_.data(), nfft_);
             // Complex multiply FIR × audio spectrum
             for (size_t i = 0; i < nfft_; i++) {
                 buf_[i] *= fir_freq_[i];
@@ -317,6 +311,6 @@ void SpectralProcessor::processBlock(float* in, float* out, size_t num_samples,
             }
         }
 
-        istftFrame(buf_, out + offset, overlap_.data());
+        istftFrame(buf_.data(), out + offset, overlap_.data());
     }
 }