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.cpp

@@ -55,7 +55,14 @@ void ReaSamplerEditor::paintSample(LICE_IBitmap* bmp, int w, int h) {
     const FaceLayout fl = faceLayout(w, h);
     const bool empty = selectedId_.empty();
 
-    paintChrome(bmp, fl, empty);
+    // Resolved ONCE per paint and handed to both bands that show it. The chrome enable and the
+    // waveform marks are two views of the same `hasLoop`, so they must not resolve it
+    // separately — and with no loop override set the resolve costs a bridge read plus a bank
+    // parse, which is not a cost to pay twice a frame.
+    SetupMarkers marks;
+    if (!empty) marks = pickedMarkers(static_cast<std::int64_t>(monoPcmFor(selectedId_).size()));
+
+    paintChrome(bmp, fl, empty, marks);
 
     // Nothing loaded: the lower bands carry the "pick a capture" prompt pointing at Browse
     // (which the chrome lit above), and there is nothing to deck.
@@ -66,7 +73,7 @@ void ReaSamplerEditor::paintSample(LICE_IBitmap* bmp, int w, int h) {
         return;
     }
 
-    paintWaveform(bmp, fl.bands.waveform);
+    paintWaveform(bmp, fl.bands.waveform, marks);
     paintDeck(bmp, fl);
 
     // The curve popup: a centered sheet over the whole face, drawn last.