feat: keep live snapshots usable through refresh failures (#149)

frontend/index.html

@@ -715,7 +715,11 @@ textarea { resize: vertical; min-height: 120px; }
     } else {
       setEventStreamStatus('Update failed · showing last activity');
     }
-    if (snapshot.freshness?.revalidating) {
+    if (snapshot.freshness?.degraded && !snapshot.freshness.revalidating) {
+      const retrySeconds = Number(snapshot.freshness.retry_in_seconds) || 0;
+      setEventStreamStatus('Refresh failed · showing last known data' +
+        (retrySeconds > 0 ? ' · retrying in ' + retrySeconds + 's' : ''));
+    } else if (snapshot.freshness?.revalidating) {
       setEventStreamStatus('Refreshing · showing recent snapshot');
     }
   }