Function isr_maintenance_selected 

pub fn isr_maintenance_selected(facts: IsrMemberFacts) -> bool

krabka’s former ISR scan rule, superseded by crate::isr::isr_candidate_selected.

The leader always stays. An in-sync follower stays exactly while Kafka’s ReplicaState.isCaughtUp holds. An out-of-sync follower is admitted when it fetched and caught up within the bound, which is not Kafka’s Partition.isFollowerInSync. The broker no longer calls this; the one remaining caller is the leader-failover model’s expansion stand-in, and this function and IsrMemberFacts go once that model moves to crate::isr::isr_candidate_selected.