fix: multi-ids duplicate only returned changes for drag-start track

The updateActiveTracks return statement was:
  return t.id === trackId ? updated : t;
This discarded duplicate items that belong to other tracks.
Fix: always return updated{ sections, midiItems, clips }
for EVERY track in the map (already sliced from originals,
so unchanged tracks are no-ops).

app/static/js/app.jsx

@@ -11741,8 +11741,7 @@ const App = () => {
                 }
               }
             });
-            var changed = t.sections && t.sections.length !== updatedSections.length;
-            return t.id === trackId ? { ...t, sections: updatedSections, midiItems: updatedMidi, clips: updatedClips } : t;
+            return { ...t, sections: updatedSections, midiItems: updatedMidi, clips: updatedClips };
           });
         });
         setDraggedSectionItem({ trackId, itemType, itemId, clickOffset, multiIds: newOriginals });