feat(map): add edge-center delta stats, thickness overlay, and layout fix

- Add edge-center sensor pair tables and delta calculations per wafer family.
- Parse and interpolate wafer thickness CSV data for offscreen visualization.
- Refactor ReadoutPanel layout using Item + anchors to fix right-margin clipping.
- Compact E-C Delta text format to fit standard sidebar width.
- Add pytest suite covering delta calculations, layout pairs, and thickness CSV.

tests/test_wafer_map_item.py

@@ -47,16 +47,89 @@ def test_thickness_properties():
 
 
 def test_thickness_setter_updates_data():
-    """Setting thicknessData updates _thickness_data."""
+    """Setting thicknessData stores [x, y, t2] triples."""
     from pygui.backend.visualization.wafer_map_item import WaferMapItem
 
     item = WaferMapItem()
     item._rebuild_thickness = MagicMock()
 
-    item.thicknessData = [1.0, 2.0, 3.0]
+    item.thicknessData = [[0.0, 10.0, 1.5], [5.0, -5.0, 2.0]]
 
-    assert item._thickness_data == [1.0, 2.0, 3.0]
+    assert item._thickness_data == [[0.0, 10.0, 1.5], [5.0, -5.0, 2.0]]
     assert item._rebuild_thickness.called
+    assert item.hasThickness is True
+
+
+THICKNESS_HEADER = "Lot Start Time,RC,Site#,Slot#,T2,NGOF,Wafer X,Wafer Y\n"
+
+
+def _write_csv(tmp_path, body, header=THICKNESS_HEADER):
+    p = tmp_path / "thickness.csv"
+    p.write_text(header + body)
+    return str(p)
+
+
+def test_parse_thickness_csv_valid(tmp_path):
+    from pygui.backend.visualization.wafer_map_item import parse_thickness_csv
+
+    path = _write_csv(tmp_path,
+                      "t,1,1,7,1.5,0,10.0,-20.0\n"
+                      "t,1,2,7,2.5,0,-30.0,40.0\n")
+    points, err = parse_thickness_csv(path)
+    assert err == ""
+    assert points == [[10.0, -20.0, 1.5], [-30.0, 40.0, 2.5]]
+
+
+def test_parse_thickness_csv_first_slot_only(tmp_path):
+    """Rows after the Slot# changes belong to another wafer and are skipped."""
+    from pygui.backend.visualization.wafer_map_item import parse_thickness_csv
+
+    path = _write_csv(tmp_path,
+                      "t,1,1,7,1.5,0,10.0,-20.0\n"
+                      "t,1,1,8,9.9,0,0.0,0.0\n")
+    points, err = parse_thickness_csv(path)
+    assert err == ""
+    assert points == [[10.0, -20.0, 1.5]]
+
+
+def test_parse_thickness_csv_bad_header(tmp_path):
+    from pygui.backend.visualization.wafer_map_item import parse_thickness_csv
+
+    path = _write_csv(tmp_path, "t,1,1,7,1.5,0,10.0,-20.0\n", header="A,B,C\n")
+    points, err = parse_thickness_csv(path)
+    assert points == []
+    assert "header" in err
+
+
+def test_parse_thickness_csv_malformed_value(tmp_path):
+    from pygui.backend.visualization.wafer_map_item import parse_thickness_csv
+
+    path = _write_csv(tmp_path, "t,1,1,7,oops,0,10.0,-20.0\n")
+    points, err = parse_thickness_csv(path)
+    assert points == []
+    assert "Malformed" in err
+
+
+def test_parse_thickness_csv_missing_file():
+    from pygui.backend.visualization.wafer_map_item import parse_thickness_csv
+
+    points, err = parse_thickness_csv("/no/such/file.csv")
+    assert points == []
+    assert "Unable to read" in err
+
+
+def test_load_thickness_slot(tmp_path):
+    """loadThickness feeds parsed points into thicknessData."""
+    from pygui.backend.visualization.wafer_map_item import WaferMapItem
+
+    item = WaferMapItem()
+    path = _write_csv(tmp_path, "t,1,1,7,1.5,0,10.0,-20.0\n")
+    assert item.loadThickness(path) == ""
+    assert item.hasThickness is True
+
+    assert item.loadThickness("/no/such/file.csv") != ""
+    # Failed load keeps the previously loaded data.
+    assert item.hasThickness is True
 
 
 def test_show_thickness_setter():