fix: Database-first cluster status detection + Stop button clarification

CRITICAL FIX (Nov 30, 2025):
- Dashboard showed 'idle' despite 22+ worker processes running
- Root cause: SSH-based worker detection timing out
- Solution: Check database for running chunks FIRST

Changes:
1. app/api/cluster/status/route.ts:
   - Query exploration database before SSH detection
   - If running chunks exist, mark workers 'active' even if SSH fails
   - Override worker status: 'offline' → 'active' when chunks running
   - Log: '✅ Cluster status: ACTIVE (database shows running chunks)'
   - Database is source of truth, SSH only for supplementary metrics

2. app/cluster/page.tsx:
   - Stop button ALREADY EXISTS (conditionally shown)
   - Shows Start when status='idle', Stop when status='active'
   - No code changes needed - fixed by status detection

Result:
- Dashboard now shows 'ACTIVE' with 2 workers (correct)
- Workers show 'active' status (was 'offline')
- Stop button automatically visible when cluster active
- System resilient to SSH timeouts/network issues

Verified:
- Container restarted: Nov 30 21:18 UTC
- API tested: Returns status='active', activeWorkers=2
- Logs confirm: Database-first logic working
- Workers confirmed running: 22+ processes on worker1, workers on worker2

cluster/collect_completed.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+"""One-time script to collect results from completed chunks"""
+
+import sys
+sys.path.insert(0, '.')
+from distributed_coordinator import DistributedCoordinator
+
+completed_chunks = {
+    'worker1': ['v9_chunk_000006', 'v9_chunk_000008'],
+    'worker2': ['v9_chunk_000000', 'v9_chunk_000007', 'v9_chunk_000009']
+}
+
+coordinator = DistributedCoordinator()
+
+for worker_id, chunks in completed_chunks.items():
+    for chunk_id in chunks:
+        print(f"📥 Collecting {chunk_id} from {worker_id}...")
+        try:
+            coordinator.collect_results(worker_id, chunk_id)
+            print(f"✅ Successfully collected {chunk_id}")
+        except Exception as e:
+            print(f"⚠️  Error collecting {chunk_id}: {e}")
+
+print("\n✅ Collection complete!")