Specify the node version in a .node-version file

This should fix the Cloudflare Pages build

.github/workflows/docs.yaml

@@ -44,7 +44,7 @@ jobs:
       - name: Install Node
         uses: actions/setup-node@v6.3.0
         with:
-          node-version: 24
+          node-version-file: .node-version
           cache: "pnpm"
 
       - name: Build the documentation