#161 · SimpleX !summarize parity: PDF attachments + YouTube/social-video transcripts

Context

SimpleX !summarize handles URLs/text only. Signal also summarizes PDF attachments, YouTube transcripts, and social-video (IG/TikTok/FB) transcripts. (Conversation-history summarization stays out — SimpleX has no durable history.)

Acceptance criteria

• [ ] !summarize on a quoted/attached PDF extracts text and summarizes it.
• [ ] !summarize <youtube-url> (and supported social-video URLs) summarizes the transcript.
• [ ] Gated on AI availability; clear message when a transcript can't be fetched.

Technical hints

• Signal reference: commands/utility/summarize.command.ts + isPdfUrl, getYouTubeTranscript, getVideoWhisperTranscript (imported in command-handler.ts).
• SimpleX target: commands/utility/summarize.command.ts (keep its documented no-history limitation).

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