Folds Filbert's N1 per Sage's comment 28355: the envelope test sends a
role cap with a tester proof. The narrowing mutant at server.mjs:50
survives the full bus suite on round 1 and is killed on round 2. Full
gate passed with the real bwrap tester case running.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
