This makes ctx.exports have the right types automatically, as long as the project has a type override like:

declare namespace Cloudflare {
  interface GlobalProps {
    // Reflects back the main module's type.
    mainModule: typeof import("./src");

    // Lists DO namespaces that are configured with storage (via `new_sqlite_classes`).
    durableNamespaces: "MyDurableObject" | "AnotherDurableObject";
  }
}

Also:

• I changed the default type for Env to be Cloudflare.Env instead of unknown in several places.
• I have added a type parameter to define ctx.props to WorkerEntrypoint and DurableObject. Unfortunately it has to be the second parameter, after Env, which is annoying since it'd be nice to leave Env as the default. Maybe if we rename these to StatelessWorker/StatefulWorker we can change the parameter order at that time to make props first?

DO NOT MERGE this until ctx.exports is verified as working in prod: I unmarked it "experimental" because otherwise it was going to be annoying to maintain separate overrides. We are very close on this so I think it'll be OK. I added back the experimental guard so that I can land this.