Fourth review round (opencode; codex hit its usage limit):
- update_identity's hot reload was always refused: the identity manager
rejects a name or hash already registered, which the running room's own
entry always is. The ACL name index then lagged the config, so a renamed
room was unmanageable by name, and a later rekey left a second live,
writable ACL. The old entry is now unregistered first and restored if
the new registration is refused (IdentityManager.unregister_identity),
and a move falls back to the store key when the name misses.
- A key change whose save and cleanup both failed left a copy at the new
key that blocked every retry. A copy under the room's own label is
replaced on retry; another identity's entries still refuse the move.
- A registration now detaches the ACL it replaces before loading, warns
when it displaces another identity sharing its hash byte, and the no-store
guard for a key change lives in LoginHelper.move_room_acl.
- /acl_stats is documented as it has always answered; store_error and
store_errors say they clear once a later read succeeds; the example
config says room servers keep their own security settings.