Function normalize_sentence 

pub fn normalize_sentence(s: &str) -> String

Normalize a sentence for map_store lookup. Rules:

• ASCII alphanumerics are kept verbatim (case preserved).
• ' and , are dropped without inserting a space, so contractions (we've → weve) and thousands separators (1,000 → 1000) stay one token.
• Any other character (whitespace, _, -, ., !, non-ASCII, …) is treated as a word boundary; runs collapse to a single space and leading/trailing spaces are trimmed.