Function select_oneshot_candidates 

pub fn select_oneshot_candidates(
    stats: &SystemdUnitStats,
    config: &UnitsConfig,
) -> Vec<String>

Select unit names whose health needs a service-type check.

Mirrors the condition in units::parse_state: only inactive, loaded .service units can be rescued by the oneshot override, so only those need the Service.Type lookup. Pure function over already collected stats, so it runs under a read lock without any I/O.