Refactor DataSource classes and enhance testing framework

- Removed outdated comments and documentation from CsvSessionSource and DemoSource classes.
- Introduced new unit tests for CsvSource and DataSource functionalities, ensuring robust validation of CSV loading and session handling.
- Added UI smoke tests to verify window instantiation and menu actions without hardware dependencies.
- Implemented VisionEngine tests to validate demo snapshots and alignment state logic.

tests/test_data_sources.py

@@ -0,0 +1,34 @@
+"""DataSource TODO anchors for future headless tests."""
+
+from __future__ import annotations
+import unittest
+
+from wafer_edge.DataSources import DemoSource, CsvSessionSource                                                 
+from wafer_edge.VisionEngine import VisionEngine                                                                
+from wafer_edge.Calibration import BaselineCalibration 
+from pathlib import Path
+import tempfile
+import MASTER_SD
+MASTER_SD = Path(__file__).resolve().parents[1] / "MASTER_SD"                                                   
+
+class DataSourcesTest(unittest.TestCase):
+    def test_demo_source_snapshot(self) -> None:
+        sources = DemoSource(VisionEngine())
+        snapshot = sources.latest_snapshot(BaselineCalibration())
+        self.assertEqual(len(snapshot.camera_readings), 4)
+        self.assertEqual(snapshot.source_label, "User App - Simulated Data")
+        self.assertLess(snapshot.sigma_mm, 0.01)
+        
+    def test_csv_session_source_snapshot(self) -> None:
+        source = CsvSessionSource(MASTER_SD, VisionEngine())
+        snapshot =  source.latest_snapshot(BaselineCalibration())
+        
+        self.assertEqual(len(snapshot.camera_readings), 4)
+        self.assertEqual(snapshot.system_status, "Ready")
+        self.assertEqual(snapshot.source_label, "Session: MASTER_SD (4 cams)")
+        
+    def test_csv_session_source_missing_or_invalid_seed(self)-> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            with self.assertRaises(FileNotFoundError):
+                CsvSessionSource(Path(tmp), VisionEngine())
+