Keep the backlog focused on deferred TESTS; the related non-test gaps
(model-allow-list, restriction-cache invalidation, server embed-recursion
guard, collectPageEmbeds cycle guard, jest DI/lib0-ESM debt) are now
tracked as issues #52-#56 and only linked from the backlog.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>