Function decide_lock_transition 

pub(super) fn decide_lock_transition(
    prev: Option<bool>,
    next: Option<bool>,
) -> Option<LockTransition>

Pure decision: given the previously-known lock state and the freshly-probed state, decide whether the transition is worth surfacing in the log.

Only transitions between confidently-known states (Some(false) ↔ Some(true)) are reportable — None → Some(true) is “we just got our first reading and it’s locked”, which we surface, but Some(true) → None → Some(true) is a flaky probe that must not generate a “unlocked / locked” log pair.