RELICARIO_TEST_PASSPHRASE and friends were checked in production code,
exposing the passphrase via /proc/<pid>/environ and shell history.
Now only compiled into debug binaries via cfg(debug_assertions) helper
functions. Release builds compile the helpers to return None, so the
env var names are absent from the release binary (verified via strings).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>