Loop: an explicit enable, four named marks with grabbable caps, and the crossfade painted where it is actually heard

hasLoop becomes user-owned with the gestures as shortcuts onto it; no format change. START uses overlay/trace, not accent/primary, which is the waveform's own fill.

src/shell/instrument/editor_paint_chrome.cpp

@@ -1,7 +1,7 @@
 // editor_paint_chrome.cpp — the CHROME band's painter: the toolbar row (product title +
-// live readout, then the control run — preview, preview-velocity knob, Mono|Stereo, Browse)
-// over the strip row, which the piano strip has to itself. Windows-only; all rects come from
-// the pure sample_chrome interior and the pure keyboard_strip geometry.
+// live readout, then the control run — preview, preview-velocity knob, Loop Off|On,
+// Mono|Stereo, Browse) over the strip row, which the piano strip has to itself. Windows-only;
+// all rects come from the pure sample_chrome interior and the pure keyboard_strip geometry.
 
 #include "shell/instrument/reasampler_editor.h"
 
@@ -94,7 +94,8 @@ void drawRootKey(LICE_IBitmap* bmp, const Rect& area, const StripLayout& sl, int
 
 }  // namespace
 
-void ReaSamplerEditor::paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool empty) {
+void ReaSamplerEditor::paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool empty,
+                                   const SetupMarkers& marks) {
     const ChromeRects& cr = fl.chrome;
 
     fillSurface(bmp, toKitBox(cr.toolbar), Role::BgPanel, InteractionState::Rest);
@@ -211,6 +212,29 @@ void ReaSamplerEditor::paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool
         }
     }
 
+    // Loop Off | On. A two-segment toggle in the same primitive as Mono|Stereo because it is
+    // the same class of control: a playback mode of the loaded capture. Outside Gate both
+    // segments draw Disabled and neither accepts a click — the state is preserved, not cleared,
+    // so the return to Gate restores it.
+    {
+        const bool live = loopControlsLive();
+        const bool on = marks.hasLoop;
+        const auto segState = [&](bool active, HoverKind hk) {
+            if (!live) return InteractionState::Disabled;
+            if (active) return InteractionState::Active;
+            return isHovered(hk, -1) ? InteractionState::Hover : InteractionState::Rest;
+        };
+        const InteractionState offState = segState(!on, HoverKind::kLoopOff);
+        const InteractionState onState = segState(on, HoverKind::kLoopOn);
+        fillSurface(bmp, toKitBox(cr.loopOff), Role::BgCell, offState);
+        fillSurface(bmp, toKitBox(cr.loopOn), Role::BgCell, onState);
+        const Role dim = live ? Role::TextPrimary : Role::TextDim;
+        kitTextCentered(bmp, cr.loopOff, "Loop Off", kToolbarFont,
+                        (live && !on) ? Role::BgBase : dim);
+        kitTextCentered(bmp, cr.loopOn, "Loop On", kToolbarFont,
+                        (live && on) ? Role::BgBase : dim);
+    }
+
     // Mono | Stereo output-mode toggle.
     {
         const bool isStereo = (channelMode_ == ChannelMode::Stereo);