Modify GitHub CI config to install uv via pipx.

This should properly fix GH-83.

.github/workflows/ci.yml

@@ -1,6 +1,6 @@
 name: Python package
 
-on: 
+on:
   push:
   pull_request:
     branches:
@@ -20,5 +20,8 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
+    - name: Install uv
+      run: |
+        pipx install uv
     - name: Run tests
       run: python run tests

run

@@ -134,12 +134,10 @@ def main(argv):
     args = parser.parse_args(argv)
 
     global uv_path
-    if args.func != run_tests:
-        # TODO(GH-83): Figure out how to get `uv` installed in the GitHub CI.
-        uv_path = shutil.which('uv')
-        if uv_path is None:
-            print('You need to have `uv` installed to run this script.')
-            sys.exit(2)
+    uv_path = shutil.which('uv')
+    if uv_path is None:
+        print('You need to have `uv` installed to run this script.')
+        sys.exit(2)
 
     global run_cmd
     if 'VIRTUAL_ENV' in os.environ:
@@ -292,9 +290,7 @@ def run_regen(args):
 
 def run_tests(args):
     del args
-    # TODO(GH-83): Figure out how to get `uv` installed on the GitHub CI.
-    # call(run_cmd + ['-m', 'unittest', 'discover', '-p', '*_test.py'])
-    call([sys.executable, '-m', 'unittest', 'discover', '-p', '*_test.py'])
+    call(run_cmd + ['-m', 'unittest', 'discover', '-p', '*_test.py'])
 
 
 def _gen_parser():