replace Redis with an embedded SQLite string->string KV store (group commit, in-tx events, SQL search)

docker/leader-election.sh

@@ -4,9 +4,10 @@
 #
 # The flock here is a MUTEX, not service discovery. It is the only thing
 # stopping two containers that mount the same /meta-core volume from putting
-# two Redis writers on one RDB/AOF. Sibling services no longer read anything
-# from this directory — they locate meta-core over UDP (meta-discovery v1, see
-# docs/project-architecture/service-discovery.md), so the kv-leader.info file
+# two writers on one database file (/meta-core/db/meta-core.db). Sibling
+# services no longer read anything from this directory — they locate meta-core
+# over UDP (beacon v2, see docs/project-architecture/beacon-v2.md), so the
+# kv-leader.info file
 # this script used to publish is gone. Keep the lock; it costs nothing and the
 # corruption it prevents is unrecoverable.
 #