Automated actions on pull requests

Pull requests should check/automate:

- Any test scripts in package.json are run
- (Report test coverage?)

- The formatter (prettier) has been run across the codebase

- (`docker compose up dev` is successful? if that's possible? or just some sanity check that it runs)

AFAIK, the way to do this is with GitHub actions

Start by inspecting the test scripts in package.json, the repository's Prettier setup, and the Docker Compose configuration for the dev service. Determine which checks are feasible in GitHub Actions, including whether coverage and a docker compose up dev sanity check are required. Done means the pull-request workflow runs the agreed checks and reports failures clearly.

Written by the indexing model from the issue text.