alice starts a session on node-1
  session_start returned HTTP 200, session_id=2a5176bc-ce80-4df3-b984-0a83f433c40c
alice writes 2 memories tagged with session_id
settle 6s for session-tagged fanout
bob lists on node-2 filtered by session_id=2a5176bc-ce80-4df3-b984-0a83f433c40c
  bob sees 2 rows tagged session_id=2a5176bc-ce80-4df3-b984-0a83f433c40c (expected 2)