The no-retained-store test asserts a negative — the tree survives — so
waiting on that negative proves nothing: settle could still remove the
tree one instant after the assertion passes. mark_session_dead now flips
a per-record settled flag once the exit rule has been applied or refused,
exposed as SessionManager::is_settled; the test waits on it before
asserting.
Refs #115
Miguel Palhas
bbafff5a98