(closes #30) add basic formatting and linting pipeline

[qdbp]

(closes #30)

this is my first naive stab at a code quality gate

I think this is quite a high priority since we're already at files with mixed indentations. barring this we're going to have a tough time keeping diff surface area low, which will make reviews painful.

any specifics (i.e. line length) obviously open for discussions

[aw632]

nit: add "closes #30" in your PR description so it gets linked

[aw632]

Thoughts on using an opinionated code formatter like black instead? that would sidestep all the discussions about line length and such.

[qdbp]

my underestanding is that ruff format is supposed to be as opinionated as black, with some slightly better defaults: https://github.com/astral-sh/ruff/blob/main/docs/formatter/black.md. Funnily enough, I think line length is the single configuration option that black has.

I was surprised to see that it supports custom indents (maybe they changed that), tbh my preference is to just use an indent of 4 -- but I don't want to just steamroll everyone on a whim either. I expect the BDFL will dictate