Every case from #6's test list: the documented-flow passes (insert-above,
the stamp, prose-only), the box#122 deletion shape, the box#118 duplicate
(proven to run before every history gate, the box#143 ordering), rc
distinctness, both STRICT degradations, the file-first-added edge, the
vacuous push-to-main shape, and the action's env wiring.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
