seo-indexabilitylisted

# seo-indexability (M2) If a page can't be crawled, indexed, or canonicalized correctly, every other signal is wasted — this is the floor under the Search score. Schema-side context: `references/schema-tier1.md`. ## Audits Working from the PageSnapshot (`rendered_dom` if present, else `raw_html`) plus response headers: 1. **Canonical**: exactly one `<link rel="canonical">`; absolute HTTPS URL; classify self-referential vs cross-domain vs chained (canonical points to a URL that itself canonicalizes elsewhere). Flag canonical that resolves to a redirect or 4xx. 2. **Canonical + noindex**: the lethal combination on the *same* URL (a noindex page used as a canonical target, or a canonicalized page also carrying noindex) — contradictory signals that drop the page. 3. **Robots directives**: `<meta name="robots">` and the `X-Robots-Tag` header for `noindex`/`nofollow`/`none`; reconcile header vs meta (header wins). 4. **Duplicate clusters**: near-identical title/H1/body across URLs with no consolidating canonical. 5. **Pagination**: paginated series signals (self-canonical per page; do not canonicalize page 2+ to page 1 — that delists deep items). 6. **Site health (covers M3)**: redirect chains/loops (>1 hop = warn, >3 hops or loop = fail), internal links returning 4xx/5xx, soft-404 (200 status on an empty/"not found" page), mixed content (HTTP subresources on HTTPS), HTTP-to-HTTPS enforcement, orphan pages (no internal inlinks), and click-depth from the homepage. ## Fixes - **AU