Add test validation CI to PRs

[tmyracle]

Continuation of #156 We should prioritize getting CI set up to run the test suite prior to merging pull requests.

Describe the solution you'd like This should help catch issues in large/complex changes that could introduce regressions. There's a good amount of complexity and side effects that can be tricky to reason about just by reading through the code.

Additional context Just burned a bunch of time trying to figure out why I couldn't complete onboarding due to a bug 😅. Running the tests and having proof of a good run prior to being able to merge could have caught this 😄.

Task list:

• [x] Create workflow yaml file
• [x] Validate runs as expected on forked repo in personal workspace
• [ ] Open PR and have Josh set up the workflow secrets/config
• [ ] Set up branch protection on main to require successful test run