fix: close review findings on the velocity-curve deck and bipolar curves

Cancels the curve-node drag whenever the popup closes so Esc mid-drag can't alias the amp curve; generalizes CurveTarget routing to one switch; fixes stale/overstated comments; clamps a pre-v12 depth fold; adds deck-inertness and filter-fold test coverage.

src/core/instrument/ui/deck_groups.cpp

@@ -238,6 +238,36 @@ bool overlayEnvInert(OverlayEnv env, bool pitchEnvEnabled, bool filterEnabled) {
     return false;  // unreachable for a valid enumerator; silences a warning.
 }
 
+bool deckKnobInert(DeckParam id, bool pitchEnvEnabled, bool filterEnabled) {
+    switch (id) {
+        case DeckParam::kPitchEnvAttack:
+        case DeckParam::kPitchEnvHold:
+        case DeckParam::kPitchEnvDecay:
+        case DeckParam::kPitchEnvDepth:
+            return !pitchEnvEnabled;
+        case DeckParam::kFilterMorph:
+        case DeckParam::kFilterCutoff:
+        case DeckParam::kFilterQ:
+        case DeckParam::kFilterDrive:
+        case DeckParam::kFilterModAmt:
+        case DeckParam::kFilterKeyTrack:
+        // The filter's velocity curve sits in the VELOCITY group but is a filter parameter:
+        // it goes inert with every other one, so no surface can reach a param the knobs can't.
+        case DeckParam::kFilterVelCurve:
+        case DeckParam::kFilterEnvAttack:
+        case DeckParam::kFilterEnvHold:
+        case DeckParam::kFilterEnvDecay:
+        case DeckParam::kFilterEnvSustain:
+        case DeckParam::kFilterEnvRelease:
+        case DeckParam::kFilterTrigAttack:
+        case DeckParam::kFilterTrigHold:
+        case DeckParam::kFilterTrigDecay:
+            return !filterEnabled;
+        default:
+            return false;
+    }
+}
+
 bool liveCommitFor(LiveDragKind kind, int paramId) {
     switch (kind) {
         case LiveDragKind::kDeckKnob:

src/core/instrument/ui/deck_groups.h

@@ -96,8 +96,10 @@ enum DeckGroupId {
 };
 
 // Which velocity curve a deck cell edits, or kNone when the control is an ordinary knob. THE
-// one place the three curve cells are named, so paint (draw a curve thumbnail, not a dial),
-// hit-test (open a popup, not start a drag) and the popup's own title all read from it.
+// one place a control id resolves to a curve target — paint (draw a curve thumbnail, not a
+// dial) and hit-test (open a popup, not start a drag) both read this predicate rather than
+// re-deriving which ids are curve cells. What each resolved target then shows (which stored
+// curve, which title) is a separate switch — see the shell's curveFor/curveTitle.
 enum class CurveTarget { kNone, kAmp, kPitch, kFilter };
 CurveTarget curveTargetFor(int controlId);
 
@@ -163,6 +165,13 @@ OverlayEnv nextOverlaySelection(OverlayEnv current, int radioId);
 // a param a knob couldn't (envelope_edit.h). Amp has no enable toggle and is never inert.
 bool overlayEnvInert(OverlayEnv env, bool pitchEnvEnabled, bool filterEnabled);
 
+// Whether a deck knob cell is drawn-but-dead: the pitch envelope's four knobs while it is
+// disabled, and the filter group's tone/modulation knobs (plus its VELOCITY cell, a filter
+// parameter that just sits in that group) while the filter is disabled. Every other id is
+// always live. Mirrors overlayEnvInert's group-toggle-gates-its-knobs shape for the deck's own
+// mouse-down/paint (the shell's deckKnobDisabled is a thin int-id wrapper over this).
+bool deckKnobInert(DeckParam id, bool pitchEnvEnabled, bool filterEnabled);
+
 // 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
 // centre can never persist a hair of modulation. Out-of-range norm clamps to the endpoints.

src/core/instrument/ui/sample_bands.h

@@ -20,7 +20,7 @@ inline constexpr int kEditorMinWidth = 840;
 inline constexpr int kEditorMinHeight = 620;
 
 // Chrome band: the toolbar row (title + nav) stacked over the control row (piano strip,
-// preview, velocity knob, curve button, channel toggle). sample_chrome partitions it.
+// preview, velocity knob, channel toggle). sample_chrome partitions it.
 inline constexpr int kTitleHeight = 26;
 inline constexpr int kChromeRowHeight = 52;