base44/javascript-sdk ? reverse-engineered prompt

Build me a JavaScript SDK for a platform called Base44, so people can use it inside generated Base44 apps or in their own frontend or backend app.

I want one simple client that can be created with an app id for external apps, and also work in Base44 apps where the client is already available. It should cover the main things a real app needs, like signing users in, managing sessions, reading and writing app data, calling backend functions, tracking analytics events, working with AI agents, handling OAuth connections, and using integrations and app logs.

Please make it feel clean and easy to use, with good TypeScript types, working tests, and a few examples that show the common cases. If you need to check the current Base44 docs online while building it, go ahead. Also include clear README docs so someone new can understand how to get started quickly.