Run scripts remotely on Microsandbox or Daytona

Scripts can now run on remote compute providers instead of the local host. Use once run --remote --compute microsandbox or once exec --remote --compute daytona, or add a remote annotation in the script header. Cache hits still replay locally, while misses stream stdout and stderr live from the provider. The Daytona adapter calls the Daytona API directly using the sandbox and API key environment variables.