Function is_prose_path 

pub fn is_prose_path(path: &str) -> bool

Return true when path is a prose / documentation file (markdown, rst, plain text, asciidoc, org).

Used to gate the L-12 cross-encoder reranker on the ripvec engine: the ms-marco-trained model helps on natural-language prose but measurably hurts code retrieval (see examples/semble_bench.rs against the semble python corpus: -0.060 NDCG@10 average across 8 repos with rerank vs without). Code corpora skip rerank; prose corpora keep it.