ci: rebuild website workflow without the texlive Docker image

The pipeline shelled out to a hand-maintained 3.4 GB texlive build-env
image on Docker Hub (last rebuilt 2019, Node ~2019). The Jun-7 Hexo 8 /
chokidar 4 upgrade needs Node >= 20.19, so that stale container failed at
'Cannot find module fs/promises'.

Replace it with a native, Docker-free workflow: checkout@v4 + setup-node@v4
(Node 22, npm cache), npm ci, build the Hexo site, and deploy over SSH with
the existing SERVER_* secrets. The website needs only Node and Python 3, so
no texlive is required. PDF/epub are no longer rebuilt in CI; the copies on
the server are left untouched (scp overwrites, never deletes) so their
download links keep working.

Author: changkun

.github/workflows/website.yml

@@ -9,21 +9,38 @@ jobs:
   build:
     name: Website
     runs-on: ubuntu-latest
-    timeout-minutes: 60
+    timeout-minutes: 20
     steps:
-      - uses: actions/checkout@v2
-      - name: build
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: npm
+          cache-dependency-path: website/package-lock.json
+
+      # The Hexo site only needs Node and Python 3 (preinstalled on the
+      # runner). The old pipeline shelled out to a hand-maintained 3.4 GB
+      # texlive Docker image just to also build the PDF/epub; that image
+      # silently drifted to a 2019 Node and broke the build. We deploy the
+      # website only here. The PDF/epub already on the server are left in
+      # place (scp overwrites, never deletes), so their download links keep
+      # working until those artifacts are rebuilt separately.
+      - name: Install website dependencies
+        run: npm ci --prefix website
+
+      - name: Build website
+        run: cd website && make
+
+      - name: Deploy to server
         env:
           USER: ${{ secrets.SERVER_USER }}
           TARGET: ${{ secrets.SERVER_PATH }}
           KEY: ${{ secrets.SERVER_KEY }}
           DOMAIN: ${{ secrets.SERVER_DOMAIN }}
         run: |
-          make build
-          mkdir ~/.ssh
+          mkdir -p ~/.ssh
           echo "$KEY" | tr -d '\r' > ~/.ssh/id_ed25519
           chmod 400 ~/.ssh/id_ed25519
-          eval "$(ssh-agent -s)"
-          ssh-add ~/.ssh/id_ed25519
-          ssh-keyscan -H $DOMAIN >> ~/.ssh/known_hosts
-          scp -r website/public/modern-cpp/* $USER@$DOMAIN:$TARGET
+          ssh-keyscan -H "$DOMAIN" >> ~/.ssh/known_hosts
+          scp -i ~/.ssh/id_ed25519 -r website/public/modern-cpp/* "$USER@$DOMAIN:$TARGET"