Add self-join to errscan hub_register() (shared template, latent gap)

bin-venus-cc: script self-registers each errscan run but does not self-join its ARO - aro:venus membership persists in hub db today, but a hub-db reset re-breaks the PM digest DM (same latent gap on @mars). Shared-template change (hub_register()), touches mars too - needs cross-project coordination, not unilateral. Non-critical per token-cut priority, park until Friday reset or hub-db reset forces it.