Function deployment_headers 

pub fn deployment_headers(
    request: &HttpRequest,
    response_head: &str,
    app_id: &str,
    mount: &str,
    identity: &str,
    secure: bool,
) -> Vec<(&'static str, String)>

Emits cache-only invalidation on successful full-page navigations to a new build. The scoped, non-authoritative marker avoids clearing cache on every interaction.