feat: smooth clock countdown for intermission and live play

Store seconds + received-at timestamp on time badge. A 1s interval
decrements locally so the clock never stutters between API polls.
Drift-corrected: always computed from the anchored API value, not
accumulated ticks. Re-render on each API response reanchors to the
real value.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/static/script.js

@@ -40,6 +40,13 @@ function renderLiveGame(game) {
 
     const dot = running ? `<span class="live-dot"></span>` : '';
 
+    // Tick the clock locally when the clock is running or during intermission
+    const shouldTick = running || intermission;
+    const rawSeconds = timeToSeconds(time);
+    const clockAttrs = shouldTick
+        ? `data-seconds="${rawSeconds}" data-received-at="${Date.now()}"`
+        : '';
+
     const hype = !intermission ? `
         <div class="hype-meter">
             <span class="hype-label">Hype Meter</span>
@@ -53,7 +60,7 @@ function renderLiveGame(game) {
             <div class="card-header">
                 <div class="badges">
                     ${periodLabel}
-                    <span class="badge">${time}</span>
+                    <span class="badge" ${clockAttrs}>${time}</span>
                 </div>
                 ${dot}
             </div>
@@ -132,6 +139,31 @@ function updateGauges() {
     });
 }
 
+// ── Clock ─────────────────────────────────────────────
+
+function timeToSeconds(str) {
+    if (!str || str === 'END') return 0;
+    const [m, s] = str.split(':').map(Number);
+    return m * 60 + s;
+}
+
+function secondsToTime(s) {
+    if (s <= 0) return 'END';
+    const m = Math.floor(s / 60);
+    const sec = s % 60;
+    return `${String(m).padStart(2, '0')}:${String(sec).padStart(2, '0')}`;
+}
+
+function tickClocks() {
+    const now = Date.now();
+    document.querySelectorAll('[data-seconds][data-received-at]').forEach(el => {
+        const seconds    = parseInt(el.dataset.seconds, 10);
+        const receivedAt = parseInt(el.dataset.receivedAt, 10);
+        const elapsed    = Math.floor((now - receivedAt) / 1000);
+        el.textContent   = secondsToTime(Math.max(0, seconds - elapsed));
+    });
+}
+
 // ── Helpers ──────────────────────────────────────────
 
 function ordinalPeriod(period) {
@@ -149,4 +181,7 @@ function autoRefresh() {
     setTimeout(autoRefresh, 5000);
 }
 
-window.addEventListener('load', autoRefresh);
+window.addEventListener('load', () => {
+    autoRefresh();
+    setInterval(tickClocks, 1000);
+});