Bump astro from 6.1.4 to 6.3.1

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 6.1.4 to 6.3.1.
- [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/astro@6.3.1/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 6.3.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -16,7 +16,7 @@
   "devDependencies": {
     "@astrojs/check": "0.9.8",
     "@astrojs/starlight": "^0.38.2",
-    "astro": "^6.1.4",
+    "astro": "^6.3.1",
     "sharp": "0.34.5",
     "typescript": "5.9.3"
   }