Function load_wallet 

pub fn load_wallet(args: &WalletArgs) -> Result<Wallet, String>

Load a wallet from an environment variable (priority) or file (fallback).

The env var is expected to contain a base58-encoded 64-byte keypair. The file is expected to be in Solana CLI JSON byte-array format ([174, 47, ...]).

Errors

Returns a human-readable error string if neither source yields a valid wallet.