fix: Use overflow-clip instead of overflow-hidden on FileCard

overflow-hidden creates a scroll container that breaks sticky positioning
for file headers. overflow-clip provides the same visual clipping for
rounded corners without affecting the scroll/sticky context.

apps/web/src/components/review/FileCard.tsx

@@ -79,7 +79,7 @@ export function FileCard({
   const tokenMap = useHighlightedFile(file.newPath, allLines);
 
   return (
-    <div className="rounded-lg border border-border overflow-hidden">
+    <div className="rounded-lg border border-border overflow-clip">
       {/* File header — sticky so it stays visible when scrolling */}
       <button
         className={`sticky z-10 flex w-full items-center gap-2 px-3 py-2 bg-muted hover:bg-muted/90 text-left text-sm font-mono transition-colors ${leftBorderClass[file.changeType]}`}