Replace Gamma?

Build me an AI slide-deck generator to replace Gamma. Requirements:

- A Node CLI around Slidev. `deck new "<topic>"` asks an LLM (key in .env) for
  an outline, then slide-by-slide content as JSON: title, bullets, speaker
  notes, layout name.
- Render that JSON to a Slidev slides.md; `deck preview` runs the Slidev dev
  server, `deck export` writes PDF and PPTX.
- Five layouts: title, bullets, two-column, big-quote, image-right. Images are
  optional via an image API key in .env; skip them cleanly when absent.
- One theme file for fonts and colors so every deck matches without redesign.
- `deck redo <n>` regenerates a single slide by number and leaves the rest
  untouched.
- Decks are files in ./decks/<slug>/ (slides.md plus assets), kept in git and
  hand-editable after generation. No database.
- No accounts, no telemetry; the only network calls are the LLM and optional
  image API.
- Out of scope: a web editor, share links with analytics, collaboration.
  slides.md in my editor is the editor.
- README: keys, export commands, and how to add a layout.