Fix VitePress build by pinning Node.js to v24

The build was failing with 'localStorage.getItem is not a function'
error in GitHub Actions using Node.js v25, while it worked locally
with Node.js v24. This appears to be a compatibility issue with
@typescript/vfs (used by @shikijs/vitepress-twoslash) in Node.js v25.

Pinning the Node.js version to v24 in the publish-docs workflow
resolves the issue.

Author: dahlia

.github/workflows/main.yaml

@@ -125,7 +125,7 @@ jobs:
     - uses: actions/checkout@v4
     - uses: actions/setup-node@v4
       with:
-        node-version: latest
+        node-version: "24"
     - uses: pnpm/action-setup@v4
       with:
         version: 10