Add no only tests to linting to avoid tests being pushed with `.only`

### Description

In all out repos, we use `eslint-plugin-no-only-tests` to avoid shipping code without tests. We should try to add that to this repo

### Epic/Story

_No response_

Start by locating the repository's ESLint configuration and lint script, then inspect how dependencies and lint rules are defined. Configure eslint-plugin-no-only-tests for this repo and verify the lint command rejects tests that use `.only`; done means the rule is active without breaking the existing lint setup.

Written by the indexing model from the issue text.