For durable code mode: a host can rerun a script after a restart and get the
same calls with the same arguments. start() runs the script with a virtual
clock (startedAt, then each result's time, never backwards), randomness from a
seed, UTC, no WeakRef/FinalizationRegistry, and the run's own tools and
globals; every call goes to onCall with the VM's call id, and the host answers
with run.deliver(seq, now, id, outcome). The VM applies results strictly in
seq order whatever the transport does, reports its fingerprint (engine
versions, prelude hash, limits) before the script runs, the calls issued after
each result (onIdle), and the result it was processing when the script ended
(result.during). Rejections can carry properties for the script's Error.
execute() is unchanged.
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.
