Enhance test strategy - use Playwright to run storybook tests and perform end-to-end tests in CI

[danielnaab]

As a project stakeholder, I would like the UI tests to be as useful as possible, while maintaining good DX.

Context: Storybook interaction tests are being used, in a preliminary way, for UI interactions. These tests are orchestrated via a helper that wraps interaction tests with vitest specs, running via JSDOM. This is great, in that we can run the tests fast in watch mode, along-side the rest of the tests in the repository. However, JSDOM is not complete, and some UI tests are not feasible with it. One such example is tests of drag-and-drop behavior in the form manager. Consider: is there a way to continue to get good DX with test suite integration, but utilizing Playwright or another approach?

Acceptance criteria:

• DnD and other JSDOM-incompatible behavior has automated coverage
• Testing approach is documented in appropriate ADRs and READMEs