Update GitHub actions

[jonmarks12]

This PR reworks the GitHub actions.
Key changes:

1. Separation of code quality checks (formatting, linting, type checking) from automated testing into distinct workflows.
2. Code quality checks are performed with the pixi lock file to ensure that consistent tooling versions across contributors.
3. Testing now is done based off pip install -e . rather than the pixi lock file. This better reflects how users actually install the package and will catch dependency issues earlier.
4. Added matrix testing for Python 3.11, 3.12, 3.13.
5. Adds CI branch to workflow triggers. Pushing to this branch will trigger workflows, enabling testing of workflow changes without opening a PR.
6. Removes redundant ci.yml workflow.

[joegomes]

LGTM!