fix: sweep select stale closure + add sweepSelectRef

handleMouseUp captured stale sweepSelect state from render
closure. Added sweepSelectRef updated on every mousemove
so mouseup reads the latest sweep range correctly.

app/static/js/app.jsx

@@ -6921,6 +6921,7 @@ const App = () => {
   const isSweepingRef = useRef(false);
   const sweepStartRef = useRef(0);
   const sweepTrackIdRef = useRef(null);
+  const sweepSelectRef = useRef(null);
   const [localSelectionTrackId, setLocalSelectionTrackId] = useState(null);
   const [localSelectionStart, setLocalSelectionStart] = useState(null);
   const [localSelectionEnd, setLocalSelectionEnd] = useState(null);
@@ -11624,7 +11625,9 @@ const App = () => {
     isSweepingRef.current = true;
     sweepStartRef.current = startTime;
     sweepTrackIdRef.current = trackId;
-    setSweepSelect({ startTime, endTime: startTime });
+    var init = { startTime, endTime: startTime };
+    sweepSelectRef.current = init;
+    setSweepSelect(init);
     setSelectedItemIds(new Set());
   };
 
@@ -11890,12 +11893,16 @@ const App = () => {
       const scrollLeft = wrapper.scrollLeft;
       const mouseX = e.clientX - rect.left + scrollLeft;
       const time = Math.max(0, mouseX / zoom - leadInMarginRef.current);
-      setSweepSelect(prev => prev ? { ...prev, endTime: time } : null);
+      setSweepSelect(prev => {
+        var updated = prev ? { ...prev, endTime: time } : null;
+        sweepSelectRef.current = updated;
+        return updated;
+      });
     };
     const handleMouseUp = () => {
       if (!isSweepingRef.current) return;
       isSweepingRef.current = false;
-      const sweep = sweepSelect;
+      const sweep = sweepSelectRef.current;
       if (sweep && sweepTrackIdRef.current) {
         const tId = sweepTrackIdRef.current;
         const start = Math.min(sweep.startTime, sweep.endTime);