fix: add .npmrc to worker/demo for frozen-lockfile compatibility

pnpm 10 defaults autoInstallPeers to true, but the lockfile was
generated with it set to false (matching root .npmrc). Adding .npmrc
to the worker ensures CI frozen-lockfile installs succeed.

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

Author: tianzhou

.github/workflows/deploy-demo.yml

@@ -31,7 +31,7 @@ jobs:
           node-version: "22"
 
       - name: Install dependencies
-        run: pnpm install
+        run: pnpm install --frozen-lockfile
         working-directory: worker/demo
 
       - name: Deploy to Cloudflare

worker/demo/.npmrc

@@ -0,0 +1 @@
+auto-install-peers=false