P4: lock PRNG prologue + correct constants (DAT_*=1); scale via prng_fvar30

CRITICAL fix: soothe_mem.bin is VA-linear (offset=RVA). DAT_18262b5c8/b704/b700
are INT 1 (cvtdq2ps -> 1.0), NOT the 0.4552/0.6089/0.6070 read earlier via a bad
section offset. Transcribed FUN_180529fe0 PRNG prologue into prng_fvar30():
fVar30=(int)(LUT[s+1]*LUT[s]+0.001). At live state 112 this is deterministically
1.0 over 300 frames, so scale level *= (1/2048)*440.95 is not randomized in
practice. Scale coefficient now computed structurally; t1kq unchanged -0.43 dB.

dsp/framed_model.hpp

@@ -23,6 +23,10 @@ struct DetectorBand {
 //   7. IIR3 leaky: twice with A3/B3
 //   8. dry/wet:    mask = mask*(fVar30*0x540888) + (1-fVar30)
 // final = min over bands.
+// PRNG (FUN_180529fe0 prologue :515-583): LCG state 0x2404e0 advances by round
+// offsets; fVar30 (scale coeff) = (int)(LUT[s+1]*LUT[s]+0.001), DAT_18262b5c8/
+// b704/b700 == 1 (VA-linear dump; earlier 0.4552/0.6089/0.6070 was a bad offset).
+// At live state 112 this yields fVar30 == 1.0 deterministically over many frames.
 class FramedDetector {
 public:
     FramedDetector(size_t nfft, float sample_rate);
@@ -36,6 +40,7 @@ private:
     size_t nfft_;
     float sample_rate_;
     double wsum_;
+    int prng_state_ = 112;  // 0x2404e0 (live snapshot value; advances per frame)
 
     std::vector<DetectorBand> bands_;
     std::vector<std::vector<float>> res_;   // per band, per bin |2B/A|