Adds mirror.list/set/delete/run ops (admin), a mirror table in OLTP, and a scheduler that pulls each configured store on its own interval. Pulls run under the store's single-writer lease and re-ingest only when artifacts actually arrived.

zitcli.Pull is the one call that cannot pass -R: zit pull refuses the flag and works by working directory. pullChanged reads zit's result positively and errors on an unrecognized line rather than defaulting to 'nothing changed', which would leave a mirror green while it silently stopped tracking. check-in: 9c7b4cff5b user: dmestas tags: trunk