fix: remove useEffect that was resetting collapsible section state

The useEffect was resetting isOpen to defaultOpen whenever files changed,
which caused the section to immediately close after clicking to open it.

Author: DevanshuNEU

frontend/src/components/DependencyGraph/ImpactPanel.tsx

@@ -115,11 +115,6 @@ function CollapsibleSection({
 }) {
   const [isOpen, setIsOpen] = useState(defaultOpen)
 
-  // Reset collapse state when file selection changes
-  useEffect(() => {
-    setIsOpen(defaultOpen)
-  }, [defaultOpen, files])
-
   const variantStyles = {
     direct: 'text-rose-600 dark:text-rose-400',
     transitive: 'text-amber-600 dark:text-amber-400',