Function relevance_score 

pub fn relevance_score(
    query: &str,
    query_terms: &[&str],
    text_lower: &str,
    importance: u8,
) -> f32

Score how well a block answers a text query.

The old ranking used depth alone, so a shallow fragment of noise always came before the exact fact the user asked for. This combines three signals:

• Phrase precision — the whole query appearing verbatim is the strongest signal; every query term appearing separately is weaker.
• Importance — the block’s recorded importance (0-10), lightly weighted.
• Specificity — a short block that is mostly the query beats a long block that merely mentions it somewhere.