Web Deploy Verification

Confirm a web/site change is ACTUALLY live in production after a merge, instead of reporting success because the merge or CI succeeded. Use after merging a PR that deploys on push (Vercel/Netlify/GitHub Actions/etc.) to a live URL, before telling a user a change has "shipped." Covers polling a live URL for content markers with a bounded background loop, a local-build Playwright screenshot fallback for visual changes (with the headless-Chromium-through-a-proxy and port-race pitfalls that break naive attempts), and why "the build succeeded" and "the deploy is live" are different claims. Complementary to product-specific deployment-testing skills (health checks, CI/CD mechan…