coinbase/coinbase-wallet-sdk ? reverse-engineered prompt

Build me a TypeScript SDK that lets a web app connect to Coinbase Wallet and Smart Wallet in a simple way.

I want developers to be able to create the SDK with an app name, open a web3 provider, ask for accounts, send requests like signing a message, and listen for wallet events like connect, disconnect, accounts changed, chain changed, and messages. It should work for desktop and mobile users, with QR code connection on desktop, deeplink support on mobile, and extension based connection when available.

Please also include a small test dapp or playground so I can try the connection flow in a browser and see the wallet connect experience end to end. Make the setup easy to run locally with the usual install and dev commands, and keep the code clean and well documented. If you need current Coinbase Wallet or Smart Wallet docs, look them up online and follow the latest guidance.