```javascript
// article.mjs
//
// NOTE ON THE PREMISE: zod (including v4) has no built-in string-to-slug
// transform — there is no `z.slug()`, no `.toSlug()`, and no `z.string().slug()`
// transform in the library. (v4 ships slug-adjacent *format validators* for
// things like nanoid/cuid/uuid, but nothing that converts arbitrary text into a
// slug.) So "exactly what zod's own slug transform produces" has no referent,
// and the two call sites cannot be made to agree by deferring to zod.
//
// The way to get byte-identical slugs in the API and the web client is to have
// exactly one implementation and import it in both places — which is what this
// module is. The algorithm is spelled out below so it can be reviewed and
// pinned; it is deterministic and Unicode-aware:
//
//   1. Unicode NFKD normalisation, then strip combining marks, so "Café"
//      folds to "cafe" rather than dropping the accented letter.
//   2. Lowercase.
//   3. Replace every run of characters that is not a Unicode letter or number
//      with a single "-". Punctuation, whitespace and emoji all collapse this
//      way, so runs of separators never produce doubled hyphens.
//   4. Trim leading and trailing "-".
//
// If you would rather match some other tool's slugs exactly (GitHub's, or
// `@sindresorhus/slugify`, or your existing database contents), replace the
// body of `slugify` — not the schema wiring — and both call sites stay in sync.

import { z } from "zod";

/** Convert arbitrary text into a URL slug. Single source of truth. */
export function slugify(input) {
  return input
    .normalize("NFKD")
    .replace(/\p{M}+/gu, "")
    .toLowerCase()
    .replace(/[^\p{L}\p{N}]+/gu, "-")
    .replace(/^-+|-+$/g, "");
}

/**
 * Accepts a string, produces its slug.
 * Slug.parse("Hello, World!") === "hello-world"
 */
export const Slug = z.string().transform(slugify);

/**
 * Article.parse({ title: "Hello, World!", slug: "Hello, World!" })
 *   === { title: "Hello, World!", slug: "hello-world" }
 */
export const Article = z.object({
  title: z.string().min(3),
  slug: Slug,
});
```

TOOLS_USED: none