MyPy: Switch to package-discovery, instead of file-discovery

This switches to using MyPy's package-discovery mechanism, having it
enumerate and then type-check everything within and under
`stanford.mais`.

(`stanford.mais` is used instead of `stanford` in case anything else
starts using that namespace.)

This is better than listing a directory to check, because it ensures
that all modules have been discovered, and their relationships laid out.

Unfortunately, although it's possible to provide a list of
files/directories in config, you can't do this with modules/packages.
I've requested support for this in python/mypy#10728

Author: akkornel

.github/workflows/main.yml

@@ -45,7 +45,7 @@ jobs:
           python -m pip install .[test]
       - name: Run MyPy
         run: |
-          mypy
+          mypy --package stanford.mais
 
   publish-test:
     name: Publish pushes to PyPi's test instance

pyproject.toml

@@ -13,9 +13,11 @@ build-backend = "setuptools.build_meta"
 namespace_packages = true
 pretty = true
 no_color_output = true
-files = [
+mypy_path = [
     "src"
 ]
+# There is no support for putting `-p` / `-package` in the MyPy config file.
+# Feature requested: https://github.com/python/mypy/issues/10728
 
 [tool.pytest.ini_options]
 testpaths = [