mu 3.13.1

jj 0.46: recreating a deleted workspace works again. A spawn that reuses
the name of a jj workspace whose directory was deleted failed on jj 0.46.

Upgrade with npm i -g @mu-crew/mu@3.13.1. No schema or extension change.

Fixed

• A jj workspace whose directory was deleted can be recreated (jj 0.46).
  mu agent spawn --workspace forgets a stale jj workspace of the same
  name first. jj 0.46 keeps printing the deleted path as the workspace
  root, so mu missed it, and in a colocated repo the workspace is also a
  Git worktree that jj workspace forget leaves registered. mu now checks
  the root on disk and runs git worktree prune after the forget, so the
  re-add no longer fails with "Workspace named … already exists" or
  "missing but already registered worktree".