fix: 修正 markdown-to-jsx 导入方式 + 新增 formatDateLabel 日期工具函数

- TextPart: default import → named import
- MaterialCard: 使用 formatDateLabel 显示今天/昨天/日期
- 清理旧测试文件，新增 ResourceTable 测试

src/web/shared/utils/time.ts

@@ -3,6 +3,23 @@ export function formatCountdown(seconds: number): string {
   return `${Math.floor(seconds / 60)}分${seconds % 60}秒`;
 }
 
+export function formatDateLabel(dateStr: string, now: Date = new Date()): string {
+  const date = new Date(dateStr);
+  if (Number.isNaN(date.getTime())) return "—";
+
+  const today = new Date(now.getFullYear(), now.getMonth(), now.getDate());
+  const yesterday = new Date(today.getTime() - 86_400_000);
+  const dateDay = new Date(date.getFullYear(), date.getMonth(), date.getDate());
+
+  if (dateDay.getTime() >= today.getTime()) return "今天";
+  if (dateDay.getTime() >= yesterday.getTime()) return "昨天";
+
+  const year = date.getFullYear();
+  const month = String(date.getMonth() + 1).padStart(2, "0");
+  const day = String(date.getDate()).padStart(2, "0");
+  return `${year}-${month}-${day}`;
+}
+
 export function formatDurationUnit(ms: null | number): { suffix: string; value: number } {
   if (ms === null) return { suffix: "", value: 0 };
   if (ms < 60000) return { suffix: "秒", value: roundToOne(ms / 1000) };