ci: install Chrome for Puppeteer in CI

Puppeteer requires a Chrome binary to be installed separately, unlike
astral which bundled its own. Add npx puppeteer browsers install step.

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

Author: bartlomieju

.github/workflows/ci.yml

@@ -50,6 +50,9 @@ jobs:
       - name: Install dependencies
         run: deno install
 
+      - name: Install Chromium for Puppeteer
+        run: npx puppeteer browsers install chrome
+
       - name: Verify formatting
         if: startsWith(matrix.os, 'ubuntu') && matrix.deno == 'v2.x'
         run: deno fmt --check