Tether Wallet Development Kit (WDK) for building non-custodial multi-chain wallets. Use when working with @tetherto/wdk-core, wallet modules (wdk-wallet-btc, wdk-wallet-evm, wdk-wallet-evm-erc-4337, wdk-wallet-solana, wdk-wallet-spark, wdk-wallet-ton, wdk-wallet-tron, ton-gasless, tron-gasfree), and protocol modules including swap (wdk-protocol-swap-velora-evm, wdk-protocol-swap-stonfi-ton), bridge (wdk-protocol-bridge-usdt0-evm), lending (wdk-protocol-lending-aave-evm), and fiat (wdk-protocol-fiat-moonpay). Covers wallet creation, transactions, token transfers, DEX swaps, cross-chain bridges, DeFi lending/borrowing, and fiat on/off ramps.