Docs: Organize Jetpack product documentation

[f]

Fixes #

Proposed changes

• Add a top-level Products branch with a catalog-backed landing page and 13 lifecycle-oriented product hubs.
• Add a Jetpack Developer Docs site adapter that owns a full-width, accessible product carousel without changing DocsPress, the DocsPress theme, or DocsPress Blocks.
• Place the site-specific carousel directly below the documentation homepage hero and keep the existing role-oriented homepage sections below it.
• Preserve all 69 baseline manifest IDs and routes while adding catalog, link, front matter, security, rendering, interaction, and deterministic-package validation.

Related product discussion/links

• None.

Does this pull request change what data or activity we track or use?

No. The carousel is navigation-only and adds no analytics, storage, or new data collection.

Testing instructions

• Run node tools/docspress/validate-developer-docs.mjs and confirm that 83 manifest pages, 69 preserved baseline routes, 13 product hubs, and one catalog-backed carousel pass.
• Run node --test tools/docspress/jetpack-developer-docs-site/tests/*.test.cjs.
• Run php tools/docspress/jetpack-developer-docs-site/tests/render-test.php.
• Run tools/docspress/jetpack-developer-docs-site/package.sh twice and confirm the generated ZIPs are byte-identical and pass unzip -t.
• Install the generated ZIP only on the mapped Jetpack Developer Docs staging site before synchronizing the homepage. Verify autoplay, hover and keyboard pause, drag suppression, reduced-motion, no-JavaScript fallback, and mobile/desktop layouts.
• Run the existing Sync developer docs to WordPress.com workflow with dry_run: true and status: publish; require zero conflicts and zero unexpected deletions before publishing.

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