👷 Run isort and mypy on just {src, tests}

Was already like this for black.
Running tox locally with a local venv in the project directory was failing
(and taking unnecessarily long)... Actually still does:
flake8 + isort + black > uv  😉

tox.ini

@@ -29,7 +29,7 @@ commands = mypy src
 [testenv:isort]
 extras = dev
 skipsdist = True
-commands = isort --check-only --diff .
+commands = isort --check-only --diff src tests
 
 [testenv:black]
 extras = dev
@@ -39,7 +39,7 @@ commands = black --check src tests docs
 [testenv:flake8]
 extras = dev
 skipsdist = True
-commands = flake8 .
+commands = flake8 src tests
 
 [testenv:docs]
 basepython=python