- Stale hashed control sockets under /tmp/meridian-<uid>/ after hard-killed
  runners: spawn-dir GC doesn't know the external endpoint. Tracked in
  GitHub issue #445 (derive control_socket_path during reaper
  reconciliation / spawn-dir pruning and unlink for terminal spawns).
- `completion_coordinator.py`, `descendant_evidence.py`, and spawn admission:
  characterize the remaining race between a qualifying final descendant snapshot and
  terminal lifecycle publication. Decide whether parent-closing admission needs a
  protocol of its own; request-sequenced refresh narrows stale evidence but is not an
  atomic admission barrier. Do not add a ledger, counter, or notification bus without
  establishing that stronger requirement.
