dbDirLeafForNetwork function
The wallet data-dir LEAF per network: a testnet proof wallet lives BESIDE a
mainnet wallet, never over it — switching defines must not hit the SDK's
NetworkMismatch on an existing mainnet DB, nor invite wiping it. Mainnet
keeps the historical zec_wallet leaf (zero migration).
Implementation
String dbDirLeafForNetwork(Network network) =>
network == Network.test ? 'zec_wallet_testnet' : 'zec_wallet';