Function live_search 

pub fn live_search(
    root: &Path,
    query: &str,
    limit: usize,
    skip: &HashSet<String>,
    deadline: Option<Instant>,
    prefilter: bool,
) -> Vec<Hit>

Layer 4: scan root live (no index required) and return ranked hits. Results are treated as the current repo, so the current-repo boost applies. skip names already-indexed files to ignore, and deadline bounds the scan — both empty/None for an unbounded scan of a never-indexed directory. When prefilter is set, only files containing the query (substring) are parsed — fast for exact/prefix/substring queries, but blind to fuzzy abbreviations, so callers retry with prefilter = false if a filtered scan finds nothing.