Fail CI release action if `gleam run -m build` produces different build artifacts.

[hayleigh-dot-dev]

A couple of times now we've published releases without first producing the server component bundle. This means users of server components often run into bugs and broken features where the Gleam code expects one thing but the client runtime is still an older verison.

It would be really helpful if our CI release action also ran gleam run -m build and compared the produced artifacts to the ones about to be published; failing in case they are not the same.