Retry forked the source run at its last checkpoint and reran the failed
stage. It now creates a new run from the source's saved spec and starts
the workflow from the beginning in a fresh workspace, as retry did
before the Petri cutover. The new run records `retried_from` and no
`fork_source_ref`.
Retry no longer needs a checkpoint, a retained workspace, or a published
run branch, so it works for any terminal run that is not archived. To
continue from where a run stopped, fork it at a checkpoint.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>