Remove transparent styling on notebook list

Fix #101607

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -304,21 +304,21 @@ export class NotebookEditorWidget extends Disposable implements INotebookEditor
 				transformOptimization: false,
 				styleController: (_suffix: string) => { return this._list!; },
 				overrideStyles: {
-					listBackground: Color.transparent,
-					listActiveSelectionBackground: Color.transparent,
+					listBackground: editorBackground,
+					listActiveSelectionBackground: editorBackground,
 					listActiveSelectionForeground: foreground,
-					listFocusAndSelectionBackground: Color.transparent,
+					listFocusAndSelectionBackground: editorBackground,
 					listFocusAndSelectionForeground: foreground,
-					listFocusBackground: Color.transparent,
+					listFocusBackground: editorBackground,
 					listFocusForeground: foreground,
 					listHoverForeground: foreground,
-					listHoverBackground: Color.transparent,
+					listHoverBackground: editorBackground,
 					listHoverOutline: focusBorder,
 					listFocusOutline: focusBorder,
-					listInactiveSelectionBackground: Color.transparent,
+					listInactiveSelectionBackground: editorBackground,
 					listInactiveSelectionForeground: foreground,
-					listInactiveFocusBackground: Color.transparent,
-					listInactiveFocusOutline: Color.transparent,
+					listInactiveFocusBackground: editorBackground,
+					listInactiveFocusOutline: editorBackground,
 				},
 				accessibilityProvider: {
 					getAriaLabel() { return null; },