perf(提交列表): 按 ↑ ↓ 换到没看过的一条也不卡了 —— 右栏预取上一条、下一条

原来换到没缓存的一条要先卸掉代码区、转圈、再整个挂回来，CPU 降速 6 倍下每次卡
60–100ms；走缓存的只换内容不卡。现在这一条加载完顺手把上下两条也拉回来，同一条
只发一次请求（预取还在路上时按到它就接着等），按住 ↓ 划过去的那些行不预取。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/oj/submission/list.vue

@@ -263,7 +263,7 @@ watch(
 
 // ==================== 选中与翻阅 ====================
 
-const { selectedId, selectedRow, position, maxPage, select, move, settleSelection, forgetJump } = useRowCursor({
+const { selectedId, selectedRow, position, neighbors, maxPage, select, move, settleSelection, forgetJump } = useRowCursor({
   rows,
   total,
   query,
@@ -858,6 +858,7 @@ function dayBreak(index: number) {
         <SubmissionPane
           v-else
           :row="selectedRow as SubmissionListItem"
+          :neighbors="neighbors as SubmissionListItem[]"
           :teacher="teacher"
           :class-name="query.className"
           :contest="inContest"
@@ -893,6 +894,7 @@ function dayBreak(index: number) {
         <SubmissionPane
           v-else
           :row="selectedRow as SubmissionListItem"
+          :neighbors="neighbors as SubmissionListItem[]"
           :teacher="teacher"
           :class-name="query.className"
           :contest="inContest"