Adds a `jekyll preview-images` command that generates front-matter-wired preview banners for posts and collections. Claude analyzes each article into an art brief and vision-reviews the render; OpenAI (default), xAI, Stability, Gemini, or a free deterministic local template produces the image. The engine is a single vendored Python file, so it also runs standalone without Ruby. Extracted from the zer0-mistakes theme and generalized: collections_dir, front_matter_key, authors_file, and collection auto-discovery make it portable to any Jekyll layout.