Vault and AgentCap

public struct AgentCap has key {
    id: UID,
    agent_id: vector<u8>,
    vault_id: ID,    // the vault this agent may act against
    policy_id: ID,   // the policy that governs it
}

Owner wallet ──owns──> OwnerCap ──authorizes──> pause / revoke / set caps / drain
                          │
Operator provisions ──> Vault (shared, multi-asset)
                          │
                        Policy (shared) ── caps, actions, scope, expiry, state
                          │
Agent key ──owns──> AgentCap ──bound to──> (vault_id, policy_id)
                          │
                  agent action ──> check_and_consume ──> coin leaves vault, or aborts