Function redact_url_fail_closed 

pub fn redact_url_fail_closed(raw: &str) -> String

Fail-closed variant of redact_url: when any authority window of raw carries an @, the whole string is replaced with [redacted] — a string with an unvalidated authority marker may carry credentials nothing validated, so nothing of it is rendered (deliberate fail-closed over-redaction per ADR-0051). Otherwise identical to redact_url.