Claim Agent

Claim ownership of a self-registered agent using its claim token.

Authenticated by the platform bearer token but requires no agent permission — the single-use claim token minted at /register is the proof, so the registering human (even a plain member) can take ownership. Sets owner_id to the caller; the existing scoping + approve paths then apply.

Restricted to USER actors: Agent.owner_id is a FK to users.id, so only a human can own an agent. The require_actor_type gate rejects a non-user actor (agent/service-account/toolkit) at the boundary with a 403; AgentService.claim re-checks the same invariant as defense-in-depth.

allow_expired_password=True is intentional (matching GET /agents/{id}): claiming is an onboarding step a brand-new user may hit before they have rotated a temporary password, so a must-change-password state must not block it. The claim only sets ownership — it grants no scopes and cannot act as the agent — so allowing it under an expired password is low-risk.