pub fn search_bm25(
query: &str,
index: &Bm25Index,
top_k: usize,
selector: Option<&[usize]>,
) -> Vec<(usize, f32)>Expand description
Top-k BM25 search with optional selector mask and zero-score
exclusion. Mirrors search.py:search_bm25.
Returns (chunk_index, score) pairs sorted by score descending.