The registry persona's traits, never a role overlay's.
Optional overlayA workflow role overlay's patch, rendered for this session only.
Optional noWhy the caller passes no key; read only when the key is null. Default 'no_user_id'.
Optional profileThe host's cognition profile. Default: the layer's.
Optional memoryThe GMI's memory manager: hydrated for the learner, and reached by forgetUser.
What the layer is told about the session a learner session serves.