Typed Metadata Helper for Pages

Build one helper that sets title, description, canonical, and Open Graph for a page. No page hand-rolls a partial tag set. FRAMEWORK [NEXT.JS APP ROUTER | ASTRO] Site name: [NAME] Default OG image: [PATH] Title pattern: [PAGE — SITE] Locales: [ONE | SEVERAL] DELIVER 1) The function or generateMetadata shape: required title and description, optional image, canonical path, noindex flag. Description length warned over 160, title warned over 60, in dev only. 2) Canonical is absolute, uses the configured site URL, and does not include tracking params. Show the strip list. 3) OG and Twitter tags that fall back to the default image, with alt text required when the image is not the default. 4) noindex for app screens, search results, and previews. A test that a private route emits noindex and a public post does not. 5) JSON-LD stays out of this helper if it is page-specific; say where it goes instead. Do not set a canonical to a different page than the one we are on unless I named a duplicate. Do not default descriptions to the title.