Can I vibecode Beautiful.ai?

Build me a Markdown slide deck tool to replace Beautiful.ai. Requirements:

- A CLI plus local preview: Node, decks are Markdown files rendered with
  reveal.js. deck serve talk.md gives a live-reload preview on localhost;
  deck export talk.md prints a PDF with Playwright.
- Slide syntax: --- starts a new slide, Note: lines become speaker notes.
- 4 layouts picked by a comment on the slide's first line: title, bullets,
  big-number, and image+text two-column. Layouts are plain CSS files I can
  edit.
- Auto-fit instead of clipping: when a slide overflows, step the text size
  down once and print a terminal warning naming the tight slides.
- theme.json for brand: two fonts, 4 colors, and a logo in the corner of
  every slide.
- Optional: deck draft "topic" < notes.txt sends my rough notes to an LLM
  (Anthropic or OpenAI key in .env) and writes a starter deck for me to
  edit; the LLM is never involved in rendering.
- Decks are plain files in a folder, fully local, no accounts, no telemetry.
- Out of scope: PPTX export and collaboration; the HTML deck plus PDF is
  enough. Do not chase Beautiful.ai's self-designing layouts, that engine is
  the product.
- README: setup and the whole slide syntax in ten lines.