Split the host into transport-independent execution logic and a VM driver, so the VM can run in a worker thread (CodemodeSandbox, unchanged), on the calling thread (InlineCodemodeSandbox), or in another isolate over RPC (RemoteCodemodeSandbox).
Add the /portable entry without Node imports and the /cloudflare entry with CodemodeSandboxDurableObject, meant to be deployed as its own Worker so scripts never block the caller's thread. Scripts that compute without awaiting a tool are bounded by an interrupt budget, now also polled while draining promise jobs. examples/cloudflare shows the setup.
