feat(ts): 实现 Polaris 可交互首页

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ts/web/nextjs/polaris/src/features/home/hooks/use-clock.ts

@@ -0,0 +1,61 @@
+"use client"
+
+import { useSyncExternalStore } from "react"
+
+import { getDelayUntilNextMinute } from "@/features/home/lib/date-time"
+
+type Listener = () => void
+
+const listeners = new Set<Listener>()
+let currentTime: Date | null = null
+let timeoutId: number | undefined
+
+function emitCurrentTime(): Date {
+  const nextTime = new Date()
+  currentTime = nextTime
+  listeners.forEach((listener) => listener())
+  return nextTime
+}
+
+function scheduleNextTick() {
+  const observedTime = emitCurrentTime()
+
+  // 每次 tick 都重新对齐；标签页休眠或主线程阻塞后不会把延迟永久带入后续分钟。
+  timeoutId = window.setTimeout(
+    scheduleNextTick,
+    getDelayUntilNextMinute(observedTime),
+  )
+}
+
+function startClock() {
+  scheduleNextTick()
+}
+
+function stopClock() {
+  if (timeoutId !== undefined) window.clearTimeout(timeoutId)
+  timeoutId = undefined
+  currentTime = null
+}
+
+function subscribe(listener: Listener) {
+  listeners.add(listener)
+  if (listeners.size === 1) startClock()
+
+  return () => {
+    listeners.delete(listener)
+    if (listeners.size === 0) stopClock()
+  }
+}
+
+function getSnapshot() {
+  return currentTime
+}
+
+function getServerSnapshot() {
+  return null
+}
+
+export function useClock(): Date | null {
+  // 服务端与 hydration 首帧固定为空；订阅建立后再读取浏览器时间，避免首屏不一致。
+  return useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot)
+}