build: move from pnpm to npm

Replace pnpm-lock.yaml with package-lock.json.

pnpm-workspace.yaml pinned npm only where cubejs depends on it
("cubejs>npm: ^11.14.1"). npm expresses that path scoping with a nested
override, so the pin stays scoped to cubejs instead of applying to every copy of
npm in the tree. Verified: cubejs is still the only overridden path.

.github/workflows/deploy.yml

@@ -22,13 +22,12 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
       - uses: actions/checkout@v7
-      - uses: pnpm/action-setup@v6
       - uses: actions/setup-node@v6
         with:
           node-version: '24'
-          cache: 'pnpm'
-      - run: pnpm install --frozen-lockfile
-      - run: pnpm build
+          cache: 'npm'
+      - run: npm ci
+      - run: npm run build
       - uses: actions/configure-pages@v6
       - uses: actions/upload-pages-artifact@v5
         with: