alice writes 5 rows into scenario38-src-81eb85
settle 4s for pre-export replication
alice exports scenario38-src-81eb85 on node-1
  export returned HTTP 200, rows_exported=171
bob imports the payload into scenario38-dst-81eb85 on node-2
  import returned HTTP 200
settle 6s for import + fanout
verify row counts match on destination
  scenario38-dst-81eb85 has 0 rows (expected 5)
  markers preserved in destination: 0/5