ci: skip node setup when already present

.gitea/workflows/test-build.yml

@@ -18,7 +18,27 @@ jobs:
         with:
           github-server-url: https://git.dumas.ddns.net
 
+      - name: Check existing Node.js
+        id: node-check
+        shell: bash
+        run: |
+          set -Eeuo pipefail
+
+          if command -v node >/dev/null 2>&1; then
+            node_version="$(node -p 'process.versions.node')"
+            node_major="${node_version%%.*}"
+
+            if [ "$node_major" = "20" ]; then
+              echo "use_existing_node=true" >> "$GITHUB_OUTPUT"
+              echo "Node.js $node_version already available; skipping setup-node"
+              exit 0
+            fi
+          fi
+
+          echo "use_existing_node=false" >> "$GITHUB_OUTPUT"
+
       - name: Setup Node.js
+        if: steps.node-check.outputs.use_existing_node != 'true'
         uses: actions/setup-node@v4
         with:
           node-version: 20
@@ -32,4 +52,3 @@ jobs:
 
       - name: Build
         run: npm run build
-