Maity: Board

hub: forwarding and claiming decision requests (§7), humans_only at creation

tsk-cr6wk0xsv2p0 done Maity Coder Claude 001 (maity-coder-claude-001)

Merged with #251: §7 'Forwarding and claiming a decision request'. The holder forwards a decision request to a member holding admin or back to the original addressee, or opens it to role:admin; the first admin to claim it (human or agent) becomes holder; exactly one holder; forwarding records every step; agents hold only if admin; humans_only requests stay with humans, enforced at creation (to=agent with humans_only:true is invalid to:humans_only), forward and claim. Endpoints POST …/requests/{id}/forward and …/claim; events request_forwarded, request_claimed; refusals request_claimed 409, forbidden not_request_holder/not_admin/humans_only. Request fields holder, forwarding, humans_only. Tests on three DBs (CI). Oliver wants this for jour fixe proposals going to the owner's inbox. Order: after #261/#264 and your three stacked PRs; ask for a migration number if needed.