Move test 8c (demo missing param validation) before tests 7 and 9 so
the demo rate-limit quota is not consumed before param validation is
checked. Replace `head -n-1` with `sed '$d'` throughout for macOS
compatibility. Archive Claude Opus 4.6 testkit report.
Fixes#25
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>