add generative evolution, cross-mod and reverb FX; expand preset bank

- 4 new params (xmod/xmix/evolve/warp) with free-running brownian evolution
- evolution: tune drift, osc2 detune sway, osc-mix crossfade, filter cutoff
  wander, resonance growl, warp drive/bias, cross-mod bloom
- per-voice unison detune spread for fat stacks
- FX engine: 3-tap ensemble chorus, filtered-feedback ping-pong delay,
  Schroeder hall reverb; new FX types 4-7 (REV HALL/ENS+REV/DLY+REV/CATHEDRAL)
- 195 presets: 40-field realignment, genre-tuned FX identities, showcase eval
- calibrate banks vs attack-inclusive peak (median 0.263); fix square-LFO
  on filter sustain collapse

Source/SynthEngine.h

@@ -14,6 +14,7 @@ struct VParams
     float vol = 0.85f, pan = 0.0f, poly = 10.f, glide = 0.f, tune = 0.f;
     float hq = 0.0f;
     float arpOn = 0, arpRate = 2, arpPattern = 0, arpOct = 1, arpGate = 70;
+    float xmod = 0, xmix = 0, evolve = 0, warp = 0;
 
     void update (const juce::AudioProcessorValueTreeState& apvts)
     {
@@ -38,6 +39,10 @@ struct VParams
         arpPattern = get ("arppattern");
         arpOct   = get ("arpoct");
         arpGate  = get ("arpgate");
+        xmod     = get ("xmod");
+        xmix     = get ("xmix");
+        evolve   = get ("evolve");
+        warp     = get ("warp");
     }
 };
 
@@ -131,12 +136,15 @@ private:
         float panL = 0.71f, panR = 0.71f;
         float curFreq = 0.0f, targetFreq = 0.0f;
         double ph1 = 0.0, ph2 = 0.0, lfoPh = 0.0;
+        double ph1r = 0.0, ph2r = 0.0;   // unwrapped phase for animated waves (FM/PWM/SUPRSW)
         float lfoSH = 0.0f;
         int   lfoIdx = 0;
         Env amp, flt;
         float lp = 0.0f, bp = 0.0f, f1c = 0.0f;
         float fcSm = 0.0f;
         float outSmooth = 0.0f;
+        float drift = 0.0f, driftT = 0.0f;   // slow random-unstable tuning wander
+        float dtSp = 0.0f;                   // unison detune spread (per voice, cents)
     };
 
     static constexpr int maxVoice = 16;
@@ -150,7 +158,12 @@ private:
     int stealIdx = 0;
     juce::Random rng;
     juce::Array<int> sustainedNotes;
+    double evoGoalT = 0.0;       // samples until the next evolution excursion
+    float evoCur = 0.0f;         // brownian wander in [-1, 1] (texture-scale)
+    float evoGoal = 0.0f;        // excursion target, re-picked every 7-18 s
+    float evoSlow = 0.0f;        // much slower wander (soundscape-scale, 1-3 min)
+    float curDetune1 = 0.0f;       // cached for noteOn (unison spread sizing)
 
-    float osc (int wave, double ph);
+    float osc (int wave, double ph, double phRaw);
     Voice* acquireVoice();
 };