Four long-running goroutines were launched with a bare go statement, so a
panic in any of them took down the whole process: the RAM cache's expired-key
eviction, the batch writer's flush worker, the disk cache cleanup worker and
the PoW memory store sweeper. Route them through util.Go.
The architecture gate only grepped for 'go func(', which is why the named-call
form went unnoticed; widen it to cover both launch styles.
Five sites used == against sentinels (redis.Nil, ingest.ErrForbidden,
errs.ErrDatabaseUninitialized). The neighbouring not-found checks already
went through errors.Is helpers, so a wrapped error would silently downgrade
a 403 to a 400 and a 500 to a 400.
ryan