onStaleJobLog property
Fires at most ONCE per session when a background-job log with the
old, pre-unique-id name (sh-<n>.log) is modified after this registry
was created — proof that another fa process on an older build shares
this directory and its job output can interleave with stale files.
Hosts surface it as a "restart that instance" hint.
Implementation
final void Function(String path)? onStaleJobLog;