fix(vst): master-gain per-sample ramp (no zipper/click); voice-count commits once on release; minor review items

src/vst/reasampler_processor.h

@@ -367,9 +367,14 @@ private:
     MonoTrigger monoTrigger_ = MonoTrigger::Retrigger;
 
     // FB1 post-mixer master gain (LINEAR; persisted in component state v8). A lock-free
-    // atomic — the ONE voice-param the audio thread reads directly (a single relaxed load
-    // per block, applied as a post-sum multiply). Default unity = pre-FB1 output.
+    // atomic — the target the UI thread writes; the audio thread ramps gainCurrent_ toward
+    // it per-sample each block (linear interpolation, ~20 ms at 48 kHz / 256-frame block)
+    // so sudden knob moves produce no zipper noise and the true-zero bottom causes no click.
     std::atomic<float> masterGain_{1.0f};
+    // The audio-thread running gain value: tracks masterGain_ across blocks, stepping at
+    // most kGainRampRate per sample toward the target. Starts at unity (pre-FB1 default).
+    // Written and read exclusively on the audio thread — no atomics needed.
+    float gainCurrent_ = 1.0f;
 
     // --- S-VIEW-4 preview-trigger mailbox (off-thread -> audio thread, lock-free) ---------
     // The editor's preview-trigger button posts a note-on/off request from the UI thread; process()