Read a task envelope

The matter handed over, as the assignee needs it: the brief with the evidence, the facts, the delegation (assignee, rule, level, the effect kinds allowed, the effective grants), the plans open and recent, the lease. An agent token reads the matters handed to it and those of the mailboxes it operates; the owner reads their own. Requires assistant:read. A matter made from authentication mail before such mail was kept out of the assistant is shown with its title, summary, ask and plan effects withheld from a reader without email:auth_secrets.