Add grid planner, CI, and tests

tests/conftest.py

@@ -0,0 +1,29 @@
+import base64
+
+import pytest
+
+from server.main import manager
+
+
+@pytest.fixture
+def fake_screenshot() -> str:
+    """Return a reproducible base64 string representing a dummy screenshot."""
+    return base64.b64encode(b"clickthrough-dummy").decode()
+
+
+@pytest.fixture
+def default_grid_request(fake_screenshot):
+    return {
+        "width": 640,
+        "height": 480,
+        "screenshot_base64": fake_screenshot,
+        "rows": 3,
+        "columns": 3,
+    }
+
+
+@pytest.fixture(autouse=True)
+def reset_manager_state():
+    manager._grids.clear()
+    yield
+    manager._grids.clear()