feat: ranking in-progress indicator persists across all admin users

- Create snapshot with status RUNNING before AI call starts
- Update to COMPLETED/FAILED when done
- Dashboard derives rankingInProgress from server snapshot status
- All admins see the spinner, not just the one who triggered it
- Poll snapshots every 3s so progress updates appear quickly

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

src/components/admin/round/ranking-dashboard.tsx

@@ -274,11 +274,17 @@ export function RankingDashboard({ competitionId: _competitionId, roundId }: Ran
   // ─── tRPC queries ─────────────────────────────────────────────────────────
   const { data: snapshots, isLoading: snapshotsLoading } = trpc.ranking.listSnapshots.useQuery(
     { roundId },
-    { refetchInterval: 30_000 },
+    // Poll every 3s so all admins see ranking progress/completion quickly
+    { refetchInterval: 3_000 },
   )
 
-  const latestSnapshotId = snapshots?.[0]?.id ?? null
-  const latestSnapshot = snapshots?.[0] ?? null
+  // Derive ranking-in-progress from server state (visible to ALL admins)
+  const rankingInProgress = snapshots?.[0]?.status === 'RUNNING'
+
+  // Find the latest COMPLETED snapshot (skip RUNNING/FAILED)
+  const latestCompleted = snapshots?.find((s) => s.status === 'COMPLETED')
+  const latestSnapshotId = latestCompleted?.id ?? null
+  const latestSnapshot = latestCompleted ?? null
 
   const { data: snapshot, isLoading: snapshotLoading } = trpc.ranking.getSnapshot.useQuery(
     { snapshotId: latestSnapshotId! },
@@ -322,20 +328,16 @@ export function RankingDashboard({ competitionId: _competitionId, roundId }: Ran
     onError: (err) => toast.error(`Failed to save: ${err.message}`),
   })
 
-  const [rankingInProgress, setRankingInProgress] = useState(false)
-
   const triggerRankMutation = trpc.ranking.triggerAutoRank.useMutation({
-    onMutate: () => setRankingInProgress(true),
     onSuccess: () => {
       toast.success('Ranking complete!')
       initialized.current = false // allow re-init on next snapshot load
       void utils.ranking.listSnapshots.invalidate({ roundId })
       void utils.ranking.getSnapshot.invalidate()
-      setRankingInProgress(false)
     },
     onError: (err) => {
       toast.error(err.message)
-      setRankingInProgress(false)
+      void utils.ranking.listSnapshots.invalidate({ roundId })
     },
   })