Function rank_memory_events 

pub fn rank_memory_events(
    events: &[MemoryEvent],
    query: &str,
    now_unix: i64,
    config: MemoryDecayConfig,
    limit: usize,
) -> Vec<ScoredMemoryEvent>

Rank memory events for a query, blending lexical relevance with exponential recency decay (#memgraphrag1). Returns at most limit events, highest score first; ties break toward the more recent event.