zapier/zapier-platform ? reverse-engineered prompt

Build me a JavaScript toolkit for creating Zapier integrations.

I want one place that gives developers a command line tool to create, test, push, and promote their apps, plus the runtime pieces those apps need when they run on Zapier. It should include a clear app schema so people can see what is allowed, and it should also handle older Legacy Web Builder apps so they keep working.

Please include a few example apps that show the basics and make it easier to get started, and set things up so the schema can be turned into TypeScript types for better developer experience. I’d also like the repo to be organized as a proper monorepo with docs, reusable packages, and easy local development. If you need current implementation details or command behavior, look up the latest docs online and follow those conventions.