Parity check: compare old and new origins before the DNS switch

How we check a migration before any DNS (Domain Name System) change. We request every known path (one per redirect rule, sitemap URLs, a short crawl) on the current host and on the Cloudflare test build, without following redirects. We compare first status, Location header, final status, and canonical and robots signals. A permanent redirect turning non-permanent, a lost redirect or a canonical change is an Error; CI (Continuous Integration) fails on any Error, and the report is kept.