OpenGraph + SEO System — Per-Page Metadata, Comprehensive Social Preview, and the Single-Source Registry Behind It

Every user-facing page now emits a complete head-metadata block: title, description, canonical URL, full OpenGraph (image, dimensions, alt, type, secure URL), Twitter card, and noindex defaults. A single component reads from a per-page registry so each surface — cover, scroll-deck variants, slide choosers, draft variants, changelog index, and changelog detail — carries its own title and description while sharing one branded social-preview image. Custom overrides are a single prop away, and adding a new gated page is a one-entry change in the registry.