Adding test for HTML in integration.yml

[VanshikaSabharwal]

Description:-
This PR primarily integrates proper HTML validation tests into the CI pipeline using Playwright, replacing the previously commented-out placeholder test logic.

Updated files

1. .github/workflows/integration.yml

• Playwright Integration (Main Change): Replaced the previously commented-out Playwright test block with a fully working implementation that:

  • Installs Playwright and Chromium
  • Starts the dev server and waits for it to respond on port 8080
  • Runs a browser test that validates the rendered HTML for: correct <title>, presence of #root div, main JS and CSS script references, and the lang="en" attribute

• macOS Fix: Split the previously combined Unix install step into separate Linux and macOS steps. Added explicit library path environment variables (DYLD_LIBRARY_PATH, LD_LIBRARY_PATH, RUSTFLAGS) for macOS and a debug step to inspect the MetaCall installation. A solution has been identified and added (run proof), with the macOS build and integration tests now passing and being further refined — which is why the pipeline progresses successfully to the next stage.

Link to the CI (where build and integration tests passes):-
https://github.com/VanshikaSabharwal/metassr/actions/runs/22988377852/job/66743756346

Link to working playwright test:-
https://github.com/VanshikaSabharwal/metassr/actions/runs/23040601286/job/66917882561

Image:-

1. Installing Playwright and Chromium

2. Run the server

3. Test HTML

[VanshikaSabharwal]

@fahdfady Please verify the content/logic, and then I will do the final cleanup to remove irrelevant code.