alice starts a session on node-1
  session_start returned HTTP 200, session_id=00f36bb7-8595-470a-b414-59ee052e59dc
alice writes 2 memories tagged with session_id
settle 6s for session-tagged fanout
bob lists on node-2 filtered by session_id=00f36bb7-8595-470a-b414-59ee052e59dc
  bob sees 2 rows tagged session_id=00f36bb7-8595-470a-b414-59ee052e59dc (expected 2)