refactor: CiEventSource gets a reference to a profile instead of owning it

refactor: make Worker::NAME be a static string

refactor: drop Worker::name, now unnecessary

refactor: QueueAdder holds an ergo::Radicle

This still loads the profile, because Worker needs a ’static lifetime and this is the easiest way to achieve that.

refactor: add ergo::Oid export

Use this consistently to reduce confusion between Oid types from Radicle.