chain_9_19: integrate into audio path with RT_CASC env gate

- Pass track_[b] from FramedDetector to process_band_structural
- chain_9_19 called when RT_CASC=1, otherwise identity (warp path)
- Uses unity track (calibrated via live-dump)
- Canon bridge 1.594 unchanged
- Requires calibration of input format for structural chain

dsp/framed_model.cpp

@@ -64,7 +64,8 @@ static void process_band_structural(
     float* mask_out,
     size_t nfft,
     float sample_rate,
-    size_t num_bands = 1
+    size_t num_bands = 1,
+    float* track = nullptr
 ) {
     const size_t half = nfft / 2;
     const size_t nbin = half + 1;
@@ -407,6 +408,17 @@ static void process_band_structural(
         f6f8[k] = 1.0f * (1.0f - mix) + mix * 0.8f;
     }
 
+    // RT_CASC=1: chain_9_19 structural path (BLOCKMAP:620-644)
+    // Replaces warp + IIR3 with calibrated chain including IIR4×2 + FIR min-phase
+    static const int casc = getenv("RT_CASC") ? atoi(getenv("RT_CASC")) : 0;
+    if (casc && track) {
+        // f6f8 is the blend buffer (step 9b accumulation)
+        // band_level is the per-band curve (VLAW or LUT output)
+        // track (from FramedDetector::track_[b]) holds persistent ACC state
+        fn529fe0::chain_9_19(band_level.data(), f6f8.data(), track,
+                              nullptr, kWarp, kRTAtt, kRTRel, nbin);
+    }
+
     for (size_t k = 0; k < nfft; k++) {
         double mm;
         // RT_FIRPOWER=1: FIR-style mask from raw spectrum.
@@ -567,17 +579,16 @@ static void process_band_structural_am(
     float sample_rate,
     size_t num_bands = 1,
     const float* casc_curve = nullptr,
-    bool use_cascade = false
+    bool use_cascade = false,
+    float* track = nullptr
 ) {
     if (use_cascade && casc_curve) {
-        // Cascade curve IS the level. Pass with res=1.0 to skip am/res division.
-        // Create a dummy res array of all 1.0
         static thread_local std::vector<float> one_res;
         size_t nbin = nfft/2 + 1;
         one_res.assign(nbin, 1.0f);
-        process_band_structural(casc_curve, one_res.data(), band, mask_out, nfft, sample_rate, num_bands);
+        process_band_structural(casc_curve, one_res.data(), band, mask_out, nfft, sample_rate, num_bands, track);
     } else {
-        process_band_structural(am, res, band, mask_out, nfft, sample_rate, num_bands);
+        process_band_structural(am, res, band, mask_out, nfft, sample_rate, num_bands, track);
     }
 }
 
@@ -771,11 +782,13 @@ void FramedDetector::processFrame(const std::complex<double>* spectrum, float* m
                         // (twin response already baked into cascade output).
                         process_band_structural_am(am_.data(), res_[b].data(), bands_[b],
                                                    band_mask.data(), nfft_, sample_rate_,
-                                                   bands_.size(), casc_curve.data(), true);
+                                                   bands_.size(), casc_curve.data(), true,
+                                                   track_[b].data());
                     }
                 } else {
                     process_band_structural(am_.data(), res_[b].data(), bands_[b],
-                                            band_mask.data(), nfft_, sample_rate_, bands_.size());
+                                            band_mask.data(), nfft_, sample_rate_, bands_.size(),
+                                            track_[b].data());
                 }
             }
             for (size_t k = 0; k <= half; k++) {