Function holds_claim 

pub fn holds_claim(
    claimed_by: &str,
    claimed_by_uid: &str,
    agent_id: &str,
    uid: Option<&str>,
) -> bool

Does a claim held by (claimed_by, claimed_by_uid) belong to the agent? Same holder rule as the store’s release (HOLDER_BY_UID): by UID when both sides have one, else by name.