create_fork copies the whole workspace inside the request, which can run
past the route timeout of an ingress in front of Windmill (Envoy's 15s
default), and the UI then reports a failure for a fork still being made.
create_fork?background=true now returns once the request is validated and
records the copy in workspace_fork_creation, which the new
fork_creation_status endpoint reads. The wizard and AI-session forks use it.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>