Propose, confirm, and execute Safe multisig transactions using the Safe{Core} SDK (protocol-kit v6 / api-kit v4). TypeScript strict. Use when an agent needs to operate a Safe smart account — (1) create/predict a new Safe, (2) fetch Safe owners/threshold/nonce, (3) list pending multisig txs, (4) build + propose a tx, (5) add confirmations, (6) execute a tx onchain, or (7) troubleshoot Safe nonce/signature issues across chains (Base/Ethereum/Optimism/Arbitrum/Polygon/etc.).