[codex] Order loops and add contributor playbook

[mberman84]

What changed

• keep featured loops pinned, then sort the remaining homepage catalog newest to oldest
• remove source links and source metadata from published loop pages and public catalogs
• preserve Hiten Shah’s full artifact-to-skill guidance in a collapsed contributor playbook
• add optional playbook schema validation, responsive rendering, and regression checks
• refresh versioned social screenshots and cache-busted assets

Why

The homepage previously preserved oldest-first source order after featured entries, and Hiten’s long-form submission was reduced to a compact prompt while its document URL was treated as a source link. This keeps the prompt bounded while publishing the useful boundaries, required outputs, implementation guidance, and reviewer handoff without exposing the document URL.

Validation

• full Loop Library generation and repository check suite
• SEO/GEO audit: 0 critical, 0 high, 0 medium findings
• worker: 14 tests passed
• 46 versioned social screenshots validated
• here.now branding validator: 96 valid credits across 48 pages
• desktop and mobile browser verification, including page 2 ordering and contributor playbook layout