Guide for building applications with the Stellar JS SDK (@stellar/stellar-sdk). Use when working with the Stellar blockchain in JavaScript/TypeScript — including sending payments, creating accounts, issuing assets, managing trustlines, trading on the DEX, querying Horizon, interacting with Stellar RPC, streaming events, building and signing transactions, multisig, claimable balances, sponsored reserves, SEP-10 auth, federation, fee-bump transactions, and interacting with Soroban smart contracts via the JS SDK. Covers all @stellar/stellar-sdk usage patterns (Horizon module, rpc module, contract module, TransactionBuilder, Keypair, Operation, Asset, etc.).