- When the `action_task` row exists but the underlying dbfs/storage blob
is gone, `OpenLogs` returns a wrapped `os.ErrNotExist` which surfaces as
a 500 on the job logs endpoints.
- Translate it to the same `util.NewNotExistErrorf` shape already used
for unknown job ids / expired logs, so both the API
(`/api/v1/repos/.../actions/jobs/<id>/logs`) and the web download
handler return a clean 404 instead.
Fixes#37990.