feat: run the per-voice filter between the pitch and amp stages, with its own deck

Params ride the one parameter set; payload v8 -> v9, off by default.
Deck composition moves to a pure deck_groups module in pitch -> filter -> amp order.

src/shell/instrument/reasampler_editor.h

@@ -14,6 +14,7 @@
 
 #include "public.sdk/source/common/pluginview.h"
 
+#include "core/instrument/ui/deck_groups.h"      // DeckParam / DeckGroupId / sampleDeckGroups
 #include "core/instrument/ui/editor_geometry.h"  // Rect (shared sub-rect type)
 #include "core/instrument/ui/envelope_edit.h"    // EnvClampBounds / NodeHit (envelope node hit-test/edit)
 #include "core/instrument/ui/envelope_overlay.h" // AmpEnvelope / EnvNode (envelope overlay draw seam)
@@ -82,31 +83,9 @@ private:
 
     // Controls on the setup surface. The int value is the opaque control id the pure
     // knob_deck hit-test returns; the shell maps it to the one parameter set or a
-    // processor-side per-instance setter.
-    enum class ParamControl {
-        kPlayMode = 0,   // Gate | Trigger toggle
-        kPitchEngine,    // Varispeed | Preserve toggle
-        kAttack,         // AHDSR attack   (Gate)  / —
-        kHold,           // AHDSR hold     (Gate)
-        kDecay,          // AHDSR decay    (Gate)
-        kSustain,        // AHDSR sustain  (Gate)
-        kRelease,        // AHDSR release  (Gate)
-        kTrigLength,     // Trigger %-length
-        kTrigFadeIn,     // Trigger fade-in
-        kTrigFadeOut,    // Trigger fade-out
-        kPitchEnvEnable, // AD pitch envelope on|off
-        kPitchEnvAttack, // AD pitch attack
-        kPitchEnvDecay,  // AD pitch decay
-        kPitchEnvDepth,  // AD pitch depth in +/- semitones
-        kKeyTrack,       // key-tracking 0..200% (lives on InstrumentParams, not PlaySeconds)
-        // Deck-only controls: processor-side per-instance params — routed to the processor
-        // setters, never through applyParamControl.
-        kVoiceCount,     // polyphony bound (1..32) — a stepped knob in the VOICE group
-        kVoiceMode,      // Poly | Mono caption toggle (VOICE group)
-        kMonoTrigger,    // Retrig | Legato row toggle (VOICE group; live only in Mono)
-        kMasterGain,     // post-mixer master gain knob (-inf..+24 dB taper, MASTER group)
-        kCount
-    };
+    // processor-side per-instance setter. The id space and the deck's group composition are
+    // the pure deck_groups module's — this alias keeps the shell's spelling.
+    using ParamControl = instrument::ui::DeckParam;
 
     // The waveform markers on the waveform band: start-point + the sustain loop's two ends,
     // in draw + hit order.
@@ -188,6 +167,10 @@ private:
     bool mouseDownDeck(const FaceLayout& fl, int x, int y);
     void mouseDownBrowse(int w, int h, int x, int y);
 
+    // Whether deck knob `id` belongs to a group whose enable toggle is off. The ONE predicate
+    // behind both the Disabled paint and the inert grab, so they cannot disagree.
+    bool deckKnobDisabled(int id) const;
+
     // Live drag resolution, split on the same axis; each handles only its own DragKind
     // values and is called from onMouseMove's router.
     void dragChrome(const FaceLayout& fl, int x, int y);   // kRootMarker
@@ -349,12 +332,6 @@ private:
     // Persisted preview velocity as a 0..1 slider value (MIDI 1..127 -> [0,1]).
     double previewVelocity01() const;
 
-    // The deck groups: AMP ENVELOPE (Gate A/H/D/S/R; Trigger Fade In/Length %/Fade Out + two
-    // reserved blanks so a mode flip never reflows neighbours) / PITCH (Key Track) / PITCH
-    // ENV (P.Attack/P.Decay/P.Depth) / VOICE (Voices knob + Poly|Mono + Retrig|Legato) /
-    // MASTER (Gain knob).
-    std::vector<DeckGroupDesc> deckGroupDescs(const PlaySeconds& play) const;
-
     // The normalized [0,1] value a deck knob shows — parameter-set ids route through
     // controlValue/keyTrack; processor-side ids (voice count, master gain, preview velocity
     // via the -2 sentinel) read the processor's live value.