One module owned every SEO primitive
Every SEO primitive lived in a single module: the canonical origin, the URL normaliser, the Open Graph and Twitter builders, and the JSON-LD factories. No page ever hardcoded the domain.
This sounds like housekeeping and it is not. One typo in a domain constant silently splits canonical signals across two hostnames, and it is close to invisible in review. Centralising made that class of bug impossible rather than unlikely.
A permanent redirect at the edge forced every apex-domain request to the www host, so link equity never split between the two.

