alice starts a session on node-1
  session_start returned HTTP 200, session_id=641e5dc8-a441-45de-810a-91f71ae0f564
alice writes 2 memories tagged with session_id
settle 6s for session-tagged fanout
bob lists on node-2 filtered by session_id=641e5dc8-a441-45de-810a-91f71ae0f564
  bob sees 2 rows tagged session_id=641e5dc8-a441-45de-810a-91f71ae0f564 (expected 2)