[Bug]: 0.19.27 server (unreleased) is not compatible with pre-0.19.27 runners

[un-def]

I'm getting this error when running a newer server with an older runner:

time=2025-09-01T16:55:06.753832-04:00 level=error msg=Exec failed err=[executor.go:371 executor.(*RunExecutor).execJob] [exec.go:12 executor.joinRelPath] path must be relative
time=2025-09-01T16:55:06.753867-04:00 level=info msg=Job state changed new=failed

Simple service configuration, working_dir unset

Originally posted by @jvstme in #3041 (comment)