fix: use single scrolling practice track

src/pages/ProcessPurposePracticePage.tsx

@@ -93,6 +93,7 @@ export default function ProcessPurposePracticePage() {
   const latestInputRef = useRef<string[]>([])
   const answerTimerRef = useRef<number | null>(null)
   const deckScrollRef = useRef<HTMLDivElement | null>(null)
+  const currentScrollLimitRef = useRef(0)
   const { practiceMode } = useAppStore()
 
   const itemMap = useMemo(
@@ -103,17 +104,9 @@ export default function ProcessPurposePracticePage() {
   const totalCount = progress.order.length
   const completedCount = progress.completedIds.length
   const isFinished = completedCount >= totalCount
-  const visibleQuestionCards = progress.order
+  const deckCards = progress.order
-    .slice(0, progress.currentIndex + 1)
     .map((id, index) => ({ item: itemMap.get(id), index }))
     .filter((card): card is { item: NonNullable<typeof currentItem>; index: number } => Boolean(card.item))
-  const nextPreviewItem = itemMap.get(progress.order[progress.currentIndex + 1])
-  const deckCards = [
-    ...visibleQuestionCards.map((card) => ({ ...card, isPreview: false })),
-    ...(nextPreviewItem
-      ? [{ item: nextPreviewItem, index: progress.currentIndex + 1, isPreview: true }]
-      : []),
-  ]
 
   const focusFirstEmptyInput = useCallback(() => {
     setTimeout(() => {
@@ -236,6 +229,7 @@ export default function ProcessPurposePracticePage() {
       const deckTop = deck.getBoundingClientRect().top
       const cardTop = currentCard.getBoundingClientRect().top
       const targetTop = Math.max(deck.scrollTop + cardTop - deckTop - 12, 0)
+      currentScrollLimitRef.current = targetTop
       deck.scrollTo({ top: targetTop, behavior: 'smooth' })
     })
   }, [progress.currentIndex])
@@ -437,6 +431,14 @@ export default function ProcessPurposePracticePage() {
     focusFirstEmptyInput()
   }, [focusFirstEmptyInput])
 
+  const handleDeckScroll = useCallback((event: React.UIEvent<HTMLDivElement>) => {
+    const deck = event.currentTarget
+    const maxScrollTop = currentScrollLimitRef.current
+    if (deck.scrollTop > maxScrollTop + 2) {
+      deck.scrollTop = maxScrollTop
+    }
+  }, [])
+
   if (!currentItem) return null
 
   return (
@@ -479,19 +481,21 @@ export default function ProcessPurposePracticePage() {
       <main className="mx-auto flex min-h-0 w-full max-w-5xl flex-1 flex-col gap-3 overflow-hidden px-4 pb-4 pt-3">
         <div
           ref={deckScrollRef}
+          onScroll={handleDeckScroll}
           className="min-h-0 flex-1 space-y-3 overflow-y-auto overscroll-contain pr-1 scroll-smooth"
         >
           <AnimatePresence initial={false}>
-            {deckCards.map(({ item, index, isPreview }) => {
+            {deckCards.map(({ item, index }) => {
               const isCurrent = index === progress.currentIndex
               const isAnsweredHistory = index < progress.currentIndex
+              const isFuture = index > progress.currentIndex
 
               return (
                 <motion.section
                   key={item.id}
                   initial={{ opacity: 0, y: 24, scale: 0.98 }}
                   animate={{
-                    opacity: isCurrent ? 1 : isPreview ? 0.52 : 0.62,
+                    opacity: isCurrent ? 1 : isFuture ? 0.42 : 0.62,
                     y: 0,
                     scale: isCurrent ? 1 : 0.975,
                   }}
@@ -503,8 +507,8 @@ export default function ProcessPurposePracticePage() {
                       ? 'border-green-300 shadow-lg shadow-green-100/70 ring-2 ring-green-100 dark:border-green-700 dark:shadow-none dark:ring-green-900/40'
                       : isCurrent
                         ? 'border-blue-200 shadow-xl shadow-blue-100/80 ring-2 ring-blue-100 dark:border-blue-800 dark:shadow-none dark:ring-blue-900/30'
-                        : isPreview
+                        : isFuture
-                          ? 'pointer-events-none border-dashed border-gray-200 bg-white/60 shadow-sm blur-[0.4px] dark:border-gray-700 dark:bg-gray-800/50'
+                          ? 'pointer-events-none border-dashed border-gray-200 bg-white/55 shadow-sm blur-[0.4px] dark:border-gray-700 dark:bg-gray-800/45'
                           : 'border-gray-100 shadow-sm dark:border-gray-800'
                   }`}
                 >
@@ -546,7 +550,7 @@ export default function ProcessPurposePracticePage() {
 
                   <p
                     className={`leading-9 text-gray-900 dark:text-gray-100 ${
-                      isCurrent ? 'text-xl' : isPreview ? 'line-clamp-2 select-none text-base text-gray-500 blur-[1.5px] dark:text-gray-400' : 'text-base'
+                      isCurrent ? 'text-xl' : isFuture ? 'line-clamp-2 select-none text-base text-gray-500 blur-[1.5px] dark:text-gray-400' : 'text-base'
                     }`}
                   >
                     {item.purpose}