Batch 18: Guards and landmines found building Batch 17

Error handling, guards and defects found by two independent code reviews while planning Batch 17 on 2026-09-10: a content validator, a built-HTML and per-crawler audit, a shared content renderer, scanner and prerender fixes. Lands when every guard is proven to fail on its target and the fixes are in production.

No due date
86% Completed