ci: rename and tweak actions.

.github/workflows/python-checks.yml

@@ -1,4 +1,4 @@
-name: Check back-end
+name: Check Python code
 
 on: [push]
 
@@ -21,6 +21,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip setuptools
         pip install -r requirements.txt -r dev-requirements.txt .
-    - name: Lint with flake8, eslint, etc.
+    - name: Lint with flake8, mypy, etc.
       run: |
-        flake8 olapy
+        flake8 olapy tests
+        mypy olapy tests

.github/workflows/python-tests.yml

@@ -1,4 +1,4 @@
-name: Check back-end
+name: Install and run Python tests
 
 on: [push]