Durable Nonce

A mechanism that replaces the short-lived recent blockhash in a transaction with a nonce value stored in a dedicated on-chain nonce account, allowing the transaction to remain valid indefinitely until it is used or the nonce is advanced. The nonce account stores the current nonce hash and an authority; the first instruction of any durable-nonce transaction must be AdvanceNonceAccount, which updates the nonce and invalidates the old one. Durable nonces are essential for workflows requiring offline signing, hardware security modules, or multi-party approval over extended time periods.