Add Playwright browser installation to Copilot setup workflow

Ensures E2E tests can be run in the Copilot agent environment by
installing Chromium browser during setup.

Co-authored-by: benbalter <282759+benbalter@users.noreply.github.com>

Author: Copilot

.github/workflows/copilot-setup-steps.yml

@@ -29,3 +29,6 @@ jobs:
 
       - name: Install dependencies
         run: npm ci
+
+      - name: Install Playwright Browsers
+        run: npx playwright install --with-deps chromium

docs/CLOUDFLARE-CACHE.md

@@ -101,6 +101,7 @@ Example workflow modification:
 ```
 
 **Trade-offs:**
+
 - **Pros**: Reduces cache purge overhead; preserves cache for unchanged content
 - **Cons**: More complex implementation; requires tracking changed files; risk of missing dependent files (e.g., a CSS file used by an HTML page)
 
@@ -148,6 +149,7 @@ For this use case (static site with content-hashed assets), `purge_everything` p
 1. Check workflow logs in GitHub Actions
 2. Verify secrets are set correctly
 3. Test API manually:
+
    ```bash
    curl -X POST "https://api.cloudflare.com/client/v4/zones/YOUR_ZONE_ID/purge_cache" \
      -H "Authorization: Bearer YOUR_API_TOKEN" \