The external `timeout`/`setsid` wrapper is GNU coreutils and absent on
macOS. When `timeout` wasn't found, run_pass captured the negated
pipeline status (0) into rc and `exit $rc` exited 0 — so the entire core
suite was silently skipped at every push on macOS, while push-check went
green. Switch to dart test's built-in --timeout, the same portable hang
guard ci/test.sh already uses; the core dart passes previously had no
per-test timeout at all. Loses the process-group SIGKILL backstop, which
only fired for a wedged PTY child that ignored the in-Dart timeout.
Co-Authored-By: Claude <noreply@anthropic.com>
