Adds MediaUrlPdf / PdfSegment to the rich-text pipeline so PDF URLs
(detected by .pdf extension, NIP-92 imeta m tag, or application/pdf
Content-Type) render a card showing the first page, filename, and page
count. Tapping opens a full-screen HorizontalPager over every page
rendered on demand with PdfRenderer. Long-press surfaces the existing
share menu. Uses only the built-in Android PdfRenderer; no new
dependencies. Desktop continues to fall back to a clickable link.
Claude
ecdbc80fc1