instrument: one staged-envelope system — per-segment curves, the sustain-less AHD, and a shared overlay for all three envelopes

Trigger's fade pair folds into the AHD (and goes live); the release anchors right;
Preserve rings its synthetic tail out instead of cutting it. Payload v10.

src/core/instrument/ui/deck_groups.h

@@ -7,7 +7,7 @@
 
 #include <vector>
 
-#include "core/instrument/engine/play_params.h"  // PlayMode (the AMP group's Gate/Trigger face)
+#include "core/instrument/engine/play_params.h"  // PlayMode (the mode-dependent group faces)
 #include "core/instrument/ui/knob_deck.h"        // DeckGroupDesc
 
 namespace reasampler::instrument::ui {
@@ -17,18 +17,20 @@ namespace reasampler::instrument::ui {
 enum class DeckParam {
     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
+    kAttack,         // amp AHDSR attack  (Gate)
+    kHold,           // amp AHDSR hold    (Gate)
+    kDecay,          // amp AHDSR decay   (Gate)
+    kSustain,        // amp AHDSR sustain (Gate)
+    kRelease,        // amp AHDSR release (Gate)
+    kTrigLength,     // Trigger play span, % of the post-start length
+    kTrigAttack,     // amp AHD attack    (Trigger)
+    kTrigHold,       // amp AHD hold, % of the span left after attack + decay
+    kTrigDecay,      // amp AHD decay     (Trigger)
+    kPitchEnvEnable, // AHD pitch envelope on|off
+    kPitchEnvAttack,
+    kPitchEnvHold,   // % of the span left after attack + decay
+    kPitchEnvDecay,
+    kPitchEnvDepth,  // AHD pitch depth in +/- semitones
     kKeyTrack,       // key-tracking 0..200% (lives on InstrumentParams, not PlaySeconds)
     // Filter. The four control positions map through filter_params' own laws; the three
     // depths are bipolar and centred at zero.
@@ -41,11 +43,32 @@ enum class DeckParam {
     kFilterVel,      // velocity -> cutoff, +/-100%
     kFilterKeyTrack, // note -> cutoff, 0..200%
     kFilterLaw,      // morph law row toggle: HP-BP-LP | HP-notch-LP
-    kFilterEnvAttack,
+    kFilterEnvAttack,   // filter AHDSR (Gate)
     kFilterEnvHold,
     kFilterEnvDecay,
     kFilterEnvSustain,
     kFilterEnvRelease,
+    kFilterTrigAttack,  // filter AHD (Trigger)
+    kFilterTrigHold,
+    kFilterTrigDecay,
+    // Curve exponents. These never get a cell of their own — each is the INNER DIAL of the
+    // stage knob it shapes (see curveParamFor), which is why only sloped stages have one.
+    kAttackCurve,
+    kDecayCurve,
+    kReleaseCurve,
+    kTrigAttackCurve,
+    kTrigDecayCurve,
+    kPitchEnvAttackCurve,
+    kPitchEnvDecayCurve,
+    kFilterEnvAttackCurve,
+    kFilterEnvDecayCurve,
+    kFilterEnvReleaseCurve,
+    kFilterTrigAttackCurve,
+    kFilterTrigDecayCurve,
+    // Overlay selection radios — transient view state, not parameters.
+    kAmpEnvSelect,
+    kPitchEnvSelect,
+    kFilterEnvSelect,
     // Deck-only controls: processor-side per-instance params — routed to the processor
     // setters, never through the parameter set.
     kVoiceCount,     // polyphony bound (1..32) — a stepped knob in the VOICE group
@@ -68,17 +91,24 @@ enum DeckGroupId {
 };
 
 // The deck's groups, left to right, in SIGNAL-FLOW order: pitch -> filter -> amp, then the
-// two instance-wide groups. `playMode` picks the AMP group's face, via knob_deck's blank-cell
-// reservation (knob_deck.h) so a mode flip never reflows the neighbouring groups.
+// two instance-wide groups. `playMode` picks the AMP and FILTER ENV groups' faces — AHDSR in
+// Gate, AHD in Trigger — via knob_deck's blank-cell reservation (knob_deck.h) so a mode flip
+// never reflows the neighbouring groups.
 std::vector<DeckGroupDesc> sampleDeckGroups(PlayMode playMode);
 
+// The curve-exponent control a stage knob's INNER DIAL edits, or kCount when the knob shapes
+// no curve. THE one place the "every stage except Hold and Sustain is sloped" rule is written
+// down: a knob with no entry here draws no inner dial and its inner region resolves as an
+// ordinary knob grab.
+DeckParam curveParamFor(DeckParam knob);
+
 // Whether control `id` is delivered LIVE — straight to the voices that are already sounding —
 // rather than through an instrument reload. The line is drawn at continuously-valued playback
 // controls, so this is a routing decision at the editor's commit site rather than a property
 // of any one knob; moving a control across the line is a change here and nowhere else.
 //
-// THE home for why each excluded control is excluded. Five continuous controls are outside the
-// live set, plus every discrete toggle:
+// THE home for why each excluded control is excluded. Three continuous controls are outside
+// the live set, plus every discrete toggle and the overlay radios:
 //   - the discrete toggles (play mode, pitch engine, filter enable/law, pitch-envelope enable)
 //     name a different sound rather than a different setting of one;
 //   - the three capture-anchored overrides (root, loop span, start frame) name positions in
@@ -86,13 +116,10 @@ std::vector<DeckGroupDesc> sampleDeckGroups(PlayMode playMode);
 //   - kKeyTrack and kFilterVel feed values a voice latches at note-on by design (the pitch
 //     ratio and the velocity-curve result), so live delivery would retune or re-gain a note
 //     already struck;
-//   - kTrigLength resolves playEnd_, a fact about the note. kTrigFadeIn/kTrigFadeOut are pure
-//     amplitude shape and would be live-able in principle, but they live in `sample.play` and
-//     are baked into SampleData at build time — the engine rebuild copies that verbatim, so
-//     only a reload can deliver them without widening LiveValues. They fold into the AHD
-//     alongside Gate's, at which point they inherit its routing; until then they reload.
-// Consequence, stated plainly: a Trigger-mode instance gets NO live delivery on its amplitude
-// controls. Only the filter and pitch-envelope knobs move a sounding Trigger one-shot.
+//   - kTrigLength resolves playEnd_, a fact about the note, not a setting of it;
+//   - the overlay radios select what the editor DRAWS and reach no parameter at all.
+// Both amp shapes are live: the Trigger fade pair that used to reload folded into the AHD and
+// inherited its routing, so a Trigger-mode instance now tracks its amplitude knobs too.
 bool isLiveDeckParam(DeckParam id);
 
 // The editor drag kinds that can commit live, in this pure module's own vocabulary (the
@@ -102,9 +129,9 @@ enum class LiveDragKind { kOther, kDeckKnob, kEnvNode };
 
 // Whether a drag of `kind` commits live. A deck knob is live per isLiveDeckParam (negative ids
 // are the shell's processor-side sentinels and out-of-range ids are not controls, so neither
-// reaches the enum); an envelope-node drag is live only in Gate, where it edits the AHDSR —
-// in Trigger the same drag rewrites the play span, which is not a live control.
-bool liveCommitFor(LiveDragKind kind, int paramId, PlayMode playMode);
+// reaches the enum); an envelope-node drag is live in either mode, since every stage value it
+// can reach — AHDSR or AHD, on any of the three envelopes — is itself live.
+bool liveCommitFor(LiveDragKind kind, int paramId);
 
 // The deck's BIPOLAR knob law: 0.5 of the knob's travel is zero depth, the ends are -1 and
 // +1. Exact inverses, and exact at the centre detent (0.5 -> 0 -> 0.5), so a knob parked at