fix: use npm install + npx wrangler for demo deploy

The wrangler-action fails because pnpm is not installed on the runner.
Switch to npm install + npx wrangler deploy, matching the stripe worker
deployment pattern.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tianzhou

.github/workflows/deploy-demo.yml

@@ -22,9 +22,16 @@ jobs:
       - name: Update image tag in wrangler.toml
         run: sed -i "s|pgplex/pgconsole:[^ \"]*|pgplex/pgconsole:${{ steps.version.outputs.VERSION }}|" worker/demo/wrangler.toml
 
-      - name: Deploy to Cloudflare
-        uses: cloudflare/wrangler-action@v3
+      - uses: actions/setup-node@v4
         with:
-          workingDirectory: worker/demo
-          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
-          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+          node-version: "22"
+
+      - name: Install dependencies
+        run: npm install --prefix worker/demo
+
+      - name: Deploy to Cloudflare
+        run: npx wrangler deploy
+        working-directory: worker/demo
+        env:
+          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          CLOUDFLARE_ACCOUNT_ID: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}