Use when a developer wants to add, write, or create an end-to-end test for an Opik feature, page, or branch — e.g. "add an e2e test for the experiments comparison page", "write a test for the feature I just built", "e2e test for this branch", "cover the dataset items flow with a test". Runs the full loop in tests_end_to_end/e2e/ — analyze the feature and frontend code, explore the live UI with the Playwright MCP, write the Page Object Model + spec, and run it locally until green.