Heartbeat honesty: SYNC badge reads refreshed_at, not grade-lock updated_at

The "SIGNAL LIVE vs STALE 8h" contradiction was a field mismatch, not a dead
pipeline. updated_at is the grade-LOCK time (advances only on a full snapshot,
5×/day — grades never change in-game, so it is intentionally stable). The
SYNC badge measured the 20-min intraday cadence (expected_interval_s=1200)
against that 5×/day field → structurally guaranteed STALE between slots even
when intraday refreshes lines perfectly.

- snapshotService: full snapshot now seeds refreshed_at at lock time
- intradayRefresh already bumps refreshed_at every ~20 min (unchanged)
- /api/snapshot/summary + GET /:sport now expose refreshed_at (was written to
  Redis but never serialized → no public liveness signal existed)
- LiveLayer SYNC badge measures freshness from refreshed_at (fallback updated_at)

Exposing refreshed_at also gives a public heartbeat probe: it advances every
intraday slot, so pipeline liveness is verifiable without container logs.

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

web/src/components/vyndr/LiveLayer.tsx

@@ -41,7 +41,12 @@ const EKG = 'M0 12 H10 L13 4 L16 20 L19 12 H30 L33 9 L36 15 L39 12 H50';
 
 interface SnapshotSummary {
   graded: number;
+  /** Grade-LOCK time — advances only on a full snapshot (5×/day). Intentionally
+   *  stable (grades never change in-game); NOT the freshness signal. */
   updated_at: string | null;
+  /** Freshness heartbeat — grade lock OR intraday line refresh (~every 20 min).
+   *  The SYNC badge keys off THIS, not updated_at. */
+  refreshed_at: string | null;
   /** The pipeline's expected cadence (s) — SYNC thresholds key off this. */
   expected_interval_s?: number;
 }
@@ -84,6 +89,7 @@ export function HeartbeatBar() {
           setSummary({
             graded: data.graded,
             updated_at: data.updated_at ?? null,
+            refreshed_at: data.refreshed_at ?? data.updated_at ?? null,
             expected_interval_s: Number(data.expected_interval_s) > 0 ? Number(data.expected_interval_s) : undefined,
           });
         }
@@ -97,7 +103,11 @@ export function HeartbeatBar() {
   }, []);
 
   void live.tick; // subscription drives the 1s clock re-render
-  const syncedAt = summary?.updated_at ? Date.parse(summary.updated_at) : NaN;
+  // Freshness is measured from the intraday heartbeat (refreshed_at), NOT the
+  // grade-lock time (updated_at). Measuring the 20-min cadence against the
+  // 5×/day lock field is what made a live pipeline read "STALE 8h".
+  const freshAt = summary?.refreshed_at ?? summary?.updated_at ?? null;
+  const syncedAt = freshAt ? Date.parse(freshAt) : NaN;
   const elapsed = Number.isFinite(syncedAt) ? Date.now() - syncedAt : null;
   const expectedMs = (summary?.expected_interval_s ?? DEFAULT_EXPECTED_S) * 1000;
   const tier: 'normal' | 'amber' | 'stale' =