Always `poetry run` commands that need a venv

It's a `Makefile` so it's handy to not have to think about if you need to be
within a poetry venv when running `make`. This commit adds a `poetry run`
before any command that needs the venv. This means that people who aren't in
a venv can just `make something` and it'll "just work", and the same is true
for those who are in a venv.