Add mypy checking to test dir and prioritize over pytest

.justfile

@@ -2,10 +2,11 @@ set dotenv-load
 
 test:
   ruff check src/smgdc
+  mypy -p src -p tests
   pytest tests -m "not extended"
-  mypy -p src
 
 test-extended:
+  mypy -p tests
   pytest tests -m extended
 
 format: