Improve plan scroll (#908)

* Done! I've removed the scrolling classes from the plan container. Plans will now use the parent chat history scroll instead of having their own nested scroll behavior.

The fix removes `max-h-[65vh] overflow-y-auto overscroll-contain` while preserving the padding and background styling.

* Cleanup script changes for task attempt 6c65f630-c1bb-4069-b3d8-7d937fc35bf7

frontend/src/components/NormalizedConversation/DisplayConversationEntry.tsx

@@ -401,12 +401,7 @@ const PlanPresentationCard: React.FC<{
         </button>
 
         {expanded && (
-          <div
+          <div className={cn('px-3 py-2', tone.contentBg)}>
-            className={cn(
-              'px-3 py-2 max-h-[65vh] overflow-y-auto overscroll-contain',
-              tone.contentBg
-            )}
-          >
             <div className={cn('text-sm', tone.contentText)}>
               <MarkdownRenderer
                 content={plan}