fix(ci): migrate workflow from npm to pnpm

.github/workflows/ci.yml

@@ -10,12 +10,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+
       - uses: actions/setup-node@v4
         with:
           node-version: 20
-          cache: npm
-      - run: npm ci
-      - run: npm run lint
+          cache: 'pnpm'
+
+      - run: pnpm install --frozen-lockfile
+
+      - run: pnpm lint
+
       # Update find roots when adding new top-level JS dirs.
       - name: Syntax check all JS
         run: find api scripts src -name '*.js' -print0 | xargs -0 -n1 node --check