Bump astro from 5.12.6 to 5.13.1 in /docs_headless

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.12.6 to 5.13.1.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/[email protected]/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.13.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

docs_headless/package.json

@@ -18,7 +18,7 @@
         "@tailwindcss/vite": "^4.1.11",
         "@types/react": "^19.1.8",
         "@types/react-dom": "^19.1.6",
-        "astro": "5.12.6",
+        "astro": "5.13.1",
         "astro-expressive-code": "^0.41.3",
         "astro-rehype-relative-markdown-links": "^0.18.1",
         "expressive-code-fullscreen": "^1.0.0",