- beachcomber and lighthouse released their savepoint whenever the inner
function reported no error; a Gate that counts a failed read as off,
or a channel function or delete snapshot that swallows one, left the
caller's Postgres transaction aborted (25P02) and failed the write
- a failed RELEASE now rolls back to the savepoint, as the READMEs promise
- beachcomber gets its testcontainers harness and sync tests
(TestSyncGates, TestSyncAfterCommit, TestSyncDeleteAndSoftDelete,
TestSyncFailuresNonFatal, TestServiceSetup); lighthouse gets
TestBroadcastSwallowedReadFailure
