Feature: Link previews (URL unfurling) #5

Summary

Add rich link previews when URLs are shared in chat messages.

Current Behavior

URLs in sioc:content are displayed as plain text or simple links.

Proposed Implementation

1. URL Detection

Parse sioc:content for URLs matching common patterns:

https?://[^\s]+

2. Metadata Fetching

Fetch Open Graph / meta tags from linked pages:

<meta property="og:title" content="..." />
<meta property="og:description" content="..." />
<meta property="og:image" content="..." />
<meta property="og:site_name" content="..." />

Fallback to:

• <title> tag
• meta[name="description"]
• First image on page

3. Preview Card UI

Display inline preview card:

┌─────────────────────────────────┐
│ 🖼️ [og:image thumbnail]        │
│ Site Name                       │
│ **Title**                       │
│ Description text...             │
└─────────────────────────────────┘

4. RDF Storage (Optional)

Cache preview data in message:

<#msg1> sioc:content "Check this out https://example.com" ;
        schema:sharedContent [
            a schema:WebPage ;
            schema:url <https://example.com> ;
            schema:name "Page Title" ;
            schema:description "..." ;
            schema:image <https://example.com/og.png>
        ] .

Considerations

• CORS: May need server-side proxy for fetching OGP
• Caching: Store previews to avoid re-fetching
• Privacy: User opt-in for auto-fetching?
• Multiple URLs: Show multiple previews or just first?

References

• Open Graph Protocol: https://ogp.me/
• Twitter Cards: https://developer.twitter.com/en/docs/twitter-for-websites/cards
• schema.org WebPage: https://schema.org/WebPage