fix(useDate): fall back to deprecated weekInfo when getWeekInfo is unavailable

deriveFirstDayOfWeek only checked Intl.Locale.getWeekInfo(), which is
absent on the older ICU shipped with current LTS Node. The v0 date
adapter already handles both forms; mirror that fallback in the helper so
locale-driven first-day derivation works in CI.

Author: claude

packages/0/src/composables/useDate/index.ts

@@ -118,8 +118,12 @@ const defaultLocales: Record<string, string> = {
  */
 function deriveFirstDayOfWeek (locale: string): number {
   try {
-    const loc = new Intl.Locale(locale) as Intl.Locale & { getWeekInfo?: () => { firstDay: number } }
-    const info = loc.getWeekInfo?.()
+    const loc = new Intl.Locale(locale) as Intl.Locale & {
+      getWeekInfo?: () => { firstDay: number }
+      weekInfo?: { firstDay: number }
+    }
+    // Newer Node/ICU exposes getWeekInfo(); older Node exposes the deprecated weekInfo property.
+    const info = loc.getWeekInfo?.() ?? loc.weekInfo
     return info ? info.firstDay % 7 : 0 // ISO 1-7 → v0 0-6
   } catch {
     return 0