ci: add clean install check

.github/workflows/ci.yml

@@ -5,6 +5,57 @@ on:
   pull_request:
 
 jobs:
+  install-check:
+    runs-on: blacksmith-4vcpu-ubuntu-2404
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: false
+
+      - name: Checkout submodules (retry)
+        run: |
+          set -euo pipefail
+          git submodule sync --recursive
+          for attempt in 1 2 3 4 5; do
+            if git -c protocol.version=2 submodule update --init --force --depth=1 --recursive; then
+              exit 0
+            fi
+            echo "Submodule update failed (attempt $attempt/5). Retrying…"
+            sleep $((attempt * 10))
+          done
+          exit 1
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          check-latest: true
+
+      - name: Runtime versions
+        run: |
+          node -v
+          npm -v
+
+      - name: Capture node path
+        run: echo "NODE_BIN=$(dirname \"$(node -p \"process.execPath\")\")" >> "$GITHUB_ENV"
+
+      - name: Enable corepack and pin pnpm
+        run: |
+          corepack enable
+          corepack prepare pnpm@10.23.0 --activate
+          pnpm -v
+
+      - name: Install dependencies (frozen)
+        env:
+          CI: true
+        run: |
+          export PATH="$NODE_BIN:$PATH"
+          which node
+          node -v
+          pnpm -v
+          pnpm install --frozen-lockfile --ignore-scripts=false --config.engine-strict=false --config.enable-pre-post-scripts=true
+
   checks:
     runs-on: blacksmith-4vcpu-ubuntu-2404
     strategy: