Function source_moved 

pub fn source_moved(
    engine: &Engine,
    resolved: &ResolvedIngest,
    workspace_root: &Path,
) -> bool

Whether any of an ingest’s sources moved since its last synced pass — the cheap, slice-free predicate the backoff uses as its additive second trigger. Compares each source’s current token to the baseline stored in the destination mem’s sync_state; a source with no baseline is not “moved” (a first sync does not by itself defeat backoff). Mirrors the plugin’s sourceChangedSince.