printf '%s' hands jq -R no line at all for an empty value; its empty output made
--argjson invalid. Seen on the first live canary-manifest run.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
(cherry picked from commit a12c8bc99d41c4f7b8e4c426d560171b2b12dd5e)