3.1. Improve acceptance test infrastructure

This project aims to improve Oppia’s acceptance test infrastructure by migrating existing tests from Puppeteer to Playwright to enhance stability, maintainability, and developer experience. The migration will be performed incrementally with dual-framework support to ensure CI stability. In addition, the project will address test flakiness by identifying and fixing persistent flaky tests, improving debugging workflows, and enhancing snapshot handling. The project also includes adding safeguards such as lint checks to prevent conflicts in shared utilities during migration. The expected outcome is a robust, maintainable, and reliable acceptance testing system with reduced flakiness and improved developer productivity