ci: switch to official GitHub Pages workflow (build + upload-pages-artifact + deploy-pages); remove legacy gh-pages deploy to avoid conflicts; no user action required

Author: lazyingart

.github/workflows/gh-pages.yml .github/workflows/pages.yml.github/workflows/gh-pages.yml renamed to .github/workflows/pages.yml

@@ -1,12 +1,21 @@
-name: Deploy fancy website
+name: GitHub Pages
 
 on:
   push:
     branches: [ main ]
   workflow_dispatch:
 
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: true
+
 jobs:
-  build-deploy:
+  build:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -29,9 +38,19 @@ jobs:
           npm install --no-save marked
           node scripts/generate_site.mjs
 
-      - name: Deploy to GitHub Pages
-        uses: peaceiris/actions-gh-pages@v3
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
         with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./docs
-          cname: ideas.onlyideas.art
+          path: ./docs
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4
+