ci(mindmodel): add scheduled validation workflow

tests/ci/test_schedule_exists.py

@@ -0,0 +1,11 @@
+import pathlib
+
+
+def test_schedule_workflow_exists():
+    path = pathlib.Path(".github/workflows/mindmodel-schedule.yml")
+    assert path.exists(), f"Expected {path} to exist"
+
+    text = path.read_text(encoding="utf-8")
+    # ensure the file is a GitHub Actions workflow that declares a schedule
+    assert "on:" in text
+    assert "schedule" in text