Better typing for $env/dynamic/*

[elliott-with-the-longest-name-on-github]

Describe the problem

When I put together the $env/dynamic/* modules, I made a stupid mistake thinking that we couldn't provide generated types similar to $env/static/*. This resulted in the dynamic modules being typed like so:

declare module '$env/dynamic/public' {
  let env: App.PublicEnv;
}
declare module '$env/dynamic/public' {
  let env: App.PrivateEnv;
}

This forces users to explicitly type their data using the App types, which is annoying -- it's "fake" type safety -- nothing is guaranteeing those keys even exist on your env object.

For some reason (maybe I was tired?) I didn't see the obvious solution...

Describe the proposed solution

declare module '$env/dynamic/public' {
  let env: {
    PUBLIC_FOO: string | undefined;
    PUBLIC_BAR: string | undefined;
    [key: string]: string;
  };
}
declare module '$env/dynamic/public' {
  let env: {
    PRIVATE_FOO: string | undefined;
    PRIVATE_BAR: string | undefined;
    [key: string]: string;
  };
}

This still allows for arbitrary optional dynamic variables (such as feature flags or environment-dependent settings), but removes the need to use "fake" types to provide autocomplete.

Alternatives considered

No response

Importance

nice to have

Additional Information

No response