Function env_name_candidates 

pub fn env_name_candidates(
    doc_text: &str,
    files: Option<&HashMap<PathBuf, String>>,
) -> Vec<Completion>

#2134: the names an env block can usefully give — each secret an actor declares (secret = "…", a Bearer, Signature or Foreign scheme) and each literal name a Secrets.get("…") reads, across the buffer and the project’s files. A lexical scan, so it works mid-edit; sorted and deduplicated.