Content authoring gaps: sales description, thumbnails/trailers, Tiptap editor, real free-preview, embed CSP

[teetangh]

Storefront-quality blockers from audit:

1. Course.description has NO authoring field → empty sales pages
2. thumbnail/trailer/logo/banner assets have zero upload paths (all gradient placeholders)
3. ARTICLE = plain textarea; Tiptap installed, no editor component exists anywhere
4. Free-preview cosmetic — player redirects unentitled users before preview matters
5. EMBED lessons blocked by our own CSP frame-src (next.config.ts:18)

• Rich description editor on course settings (shared with Live defense engine — AI-assisted project defense (AVNI-style) #3 renderer)
• Shared media-picker → public-assets bucket for thumbnails/logos/banners; trailer via existing video flows
• TiptapEditor client comp + sanitized server-safe renderer
• Preview: marketing detail page lists isFreePreview lessons with inline playback; ?preview=1 deep link gated to preview lessons only
• frame-src allowlist (youtube-nocookie, player.vimeo.com, docs.google) + host validation in upsertLesson

Spec: temp prompt library 08-content-authoring.