add memory review pass (dream/distill)
structurally matches claude code's /dream skill: write-time is fast
and might be wrong (extraction pipeline), review-time is slow and
has distance (this).
process_review() gathers recent active observations across all user
namespaces, asks a review agent to evaluate each with distance from
the original conversation, and applies the decisions:
- keep: observation stays as-is
- supersede: marked superseded, stops appearing in context
- promote: creates a public cosmik card on semble
new endpoint: POST /api/control/review (bearer auth, same pattern
as /post and /explore). no scheduled slot yet — operator-triggered.