Lohnt sich dein eigenes MagicSlides?

Build me an AI presentation generator to replace MagicSlides, in an empty repo.

Stack (no alternatives): a Node.js + TypeScript CLI. Use pptxgenjs for PPTX output
and LibreOffice headless (soffice --headless --convert-to pdf) for the PDF. Do not
build a web app.

Core loop:
- `deck new "<topic>"` OR `deck new --url <article-url>` OR `deck new --yt <youtube-url>`.
- For --url, fetch and strip the page to text; for --yt, pull the transcript via the
  youtube-transcript package; for a bare topic, skip fetching.
- Send that text to an LLM (key in .env) and ask for structured JSON: a deck title,
  then per slide a title, 3-5 bullets, and speaker notes.
- Render the JSON with pptxgenjs using one of five layouts: title, bullets,
  two-column, section-break, quote.
- Write ./decks/<slug>/deck.pptx, deck.pdf, and the raw slides.json.

Details:
- One theme file (fonts, colors, logo) so every deck is consistent; no per-deck design.
- `deck redo <n>` regenerates a single slide by number, leaving the rest untouched.
- Decks are plain files on disk, git-friendly and hand-editable. No database.
- Secrets (LLM key, optional image API key) live in .env; ship .env.example.
- No accounts, no telemetry; the only network calls are the LLM, the optional image
  API, and the URL/YouTube fetch.
- Out of scope: a web editor, a Google Slides add-on, a browser extension, hosted
  share links, collaboration. Editing the PPTX in Keynote/PowerPoint is the editor.
- README: keys, the three input modes, export commands, and how to add a layout.