feat: add SEO foundation dimension (scoring model v1.4)

[ryanportfolio]

What

Adds a ninth weighted dimension, SEO foundation (weight: low), and bumps the scoring model to v1.4.0.

Deliberately narrow: presence/length of title, description and canonical are already scored under topical focus & metadata. This dimension covers the cross-cutting failures single-page checks cannot see:

• Canonical self-consistency: a canonical pointing away from the audited page means every consumer that honors it attributes the content to a different URL (www/slash/scheme variants are tolerated).
• Title and meta-description uniqueness across the fetched pages: duplicated metadata makes distinct pages indistinguishable to a retriever.

Also folds an unscored heading-hierarchy advisory (skipped levels, e.g. H2 to H4) into answer-readiness.

Deliberately excluded

Core Web Vitals, backlinks, mobile rendering, hreflang: classic SEO with near-zero GEO signal, and out of mission for a citation-readiness audit.

Scoring model

• Version 1.3.0 to 1.4.0 (scores comparable only within a version).
• Golden pins recalibrated: the three pinned overalls are unchanged (99/33/25); each context gains a seoFoundation score (100/30/30).
• The good-article fixture's canonical was corrected to be self-referencing (it previously pointed at a foreign host, which the new check rightly flags).

Docs

README and site copy (index/about/audit app shell) updated from eight to nine dimensions.

Verification

• npx tsc --noEmit: clean
• npx vitest run: 161/161 pass

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