Checks identity and reference consistency after presentation shape validation.

Navigation groups may omit content when they have children. Absolute HTTP(S) links may refer to another site; other navigation leaves and search results need local content. IDs are unique within each index, and navigation/search paths for a shared ID must agree. Content need not appear in either index.

Backlink targets must be local content. Their origins may belong to a host's wider graph, but a known origin cannot contradict its indexed path. This deliberately does not parse document links or impose a host routing policy.