Add Playwright timeline height parity tests to CI

- add browser E2E tests validating timeline height estimator against rendered DOM
- configure Playwright test runner and scripts in `apps/web`
- run browser tests in CI with Playwright browser caching and install step
5470801c4aJulius Marminge committed on 3/5/2026, 6:20:34 PM· committed by Julius Marmingeparent2ad2d3e
6 files changedLine totals unavailable