Reflow the deck into two categorical rows plus a double-height MASTER bus deck

Row membership is now the group's own property, not a wrap outcome. FILTER's Band|Notch moves to its caption slack, which is what makes the sound row fit. MASTER gains the limiter toggle, the output meter and the GR lamp.

src/core/instrument/ui/deck_groups.cpp

@@ -11,9 +11,14 @@ int id(DeckParam p) { return static_cast<int>(p); }
 double clamp(double v, double lo, double hi) { return v < lo ? lo : (v > hi ? hi : v); }
 
 // Segment width of the three Staged|Spline toggles. Sized so each env group's caption row stays
-// no wider than its knob row — the ceiling is PITCH ENV's, whose caption row lands exactly on
-// its four-cell knob row at 23. Raising it reflows the deck's first row.
+// no wider than its knob row; the binding group is PITCH ENV, which reaches its four-cell knob
+// row at 47 (AMP, the next tightest, at 55). Well inside the ceiling — raising it would widen
+// the CONTOUR row, which has 144px of slack, not the SOUND row.
 constexpr int kEnvModeSegW = 23;
+
+// The output meter's column, right of MASTER's cell slots. 62 + the 60px cell + the gap + the
+// group's own padding is exactly kDeckSpanningW.
+constexpr int kMasterMeterW = 62;
 }  // namespace
 
 double deckBipolarFromNorm(double norm) { return clamp(norm, 0.0, 1.0) * 2.0 - 1.0; }
@@ -63,7 +68,9 @@ std::vector<DeckGroupDesc> sampleDeckGroups(PlayMode playMode) {
                           id(DeckParam::kFilterModAmt),
                           id(DeckParam::kFilterVel),
                           id(DeckParam::kFilterKeyTrack)};
-        filter.rowToggle = {id(DeckParam::kFilterLaw), 44};
+        // The morph law rides the caption slack. Moving it back to the knob row costs the
+        // group 92px and the SOUND row stops fitting its block.
+        filter.captionToggle2 = {id(DeckParam::kFilterLaw), 44};
         out.push_back(std::move(filter));
     }
     {
@@ -126,12 +133,19 @@ std::vector<DeckGroupDesc> sampleDeckGroups(PlayMode playMode) {
         out.push_back(std::move(voice));
     }
     {
+        // The lower slot is reserved and draws NOTHING: blank reads as breathing room where a
+        // dashed placeholder would read as unfinished. It is one cell, not two — a second
+        // would spend 60 of the layout's whole 90px budget on a control nobody has named.
         DeckGroupDesc master;
         master.id = kGroupMaster;
         master.captionWidth = 46;
-        master.cellIds = {id(DeckParam::kMasterGain)};
+        master.captionRadio = {id(DeckParam::kMasterGr), /*passive=*/true};
+        master.captionToggle = {id(DeckParam::kLimiterEnable), 32};
+        master.cellIds = {id(DeckParam::kMasterGain), -1};
+        master.column = {id(DeckParam::kMasterMeter), kMasterMeterW};
         out.push_back(std::move(master));
     }
+    for (DeckGroupDesc& d : out) d.row = deckRowFor(static_cast<DeckGroupId>(d.id));
     return out;
 }
 
@@ -257,6 +271,11 @@ LiveCommit deckParamCommit(DeckParam id) {
         case DeckParam::kVoiceMode:
         case DeckParam::kMonoTrigger:
         case DeckParam::kMasterGain:
+        case DeckParam::kLimiterEnable:
+        // MASTER's two readouts reach no parameter at all — the same footing as the overlay
+        // radios above.
+        case DeckParam::kMasterMeter:
+        case DeckParam::kMasterGr:
         case DeckParam::kCount:  // not a control
             return LiveCommit::Reload;
     }