Fix test failures after styled-components migration

- Update Toast.spec.tsx to check data-fading-out attribute instead of
  isFadingOut prop, matching the new plain CSS implementation
- Update index.spec.tsx to query elements by data-testid and aria-label
  instead of styled-component types (BannerBodyWrapper, CloseButton)
- Remove import of deleted styles.tsx file from index.spec.tsx
- Delete unused styles.tsx file as specified in migration plan

All tests now query the actual DOM elements using their attributes,
which aligns with the plain CSS migration approach.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: OpenStaxClaude

src/app/notifications/components/ToastNotifications/Toast.spec.tsx

@@ -82,7 +82,7 @@ describe('Toast', () => {
 
     const bannerBody = component.root.findByProps({'data-testid': 'banner-body'});
 
-    expect(bannerBody.props.isFadingOut).toBe(true);
+    expect(bannerBody.props['data-fading-out']).toBe(true);
 
     component.unmount();
   });
@@ -98,7 +98,7 @@ describe('Toast', () => {
 
     const bannerBody = component.root.findByProps({'data-testid': 'banner-body'});
 
-    expect(bannerBody.props.isFadingOut).toBe(false);
+    expect(bannerBody.props['data-fading-out']).toBe(false);
 
     component.unmount();
   });
@@ -135,7 +135,7 @@ describe('Toast', () => {
       assertWindow().dispatchEvent(event);
     });
 
-    expect(bannerBody.props.isFadingOut).toBe(true);
+    expect(bannerBody.props['data-fading-out']).toBe(true);
 
     component.unmount();
   });
@@ -157,15 +157,15 @@ describe('Toast', () => {
       assertWindow().dispatchEvent(event);
     });
 
-    expect(bannerBody.props.isFadingOut).toBe(true);
+    expect(bannerBody.props['data-fading-out']).toBe(true);
 
     renderer.act(() => {
       component.update(<TestContainer>
         <Toast dismiss={dismiss} notification={{...toast, timestamp: Date.now() + 10}} positionProps={position} />
       </TestContainer>);
     });
 
-    expect(bannerBody.props.isFadingOut).toBe(false);
+    expect(bannerBody.props['data-fading-out']).toBe(false);
     component.unmount();
   });
 

src/app/notifications/components/ToastNotifications/index.spec.tsx

@@ -9,7 +9,6 @@ import { AppState, Store } from '../../../types';
 import { addToast, dismissNotification } from '../../actions';
 import { toastNotifications } from '../../selectors';
 import { toastMessageKeys } from './constants';
-import { BannerBodyWrapper, CloseButton } from './styles';
 import Toast from './Toast';
 
 jest.mock('react', () => {
@@ -69,31 +68,31 @@ describe('ToastNotifications', () => {
       <ToastNotifications />
     </TestContainer>);
 
-    expect(root.findAllByType(BannerBodyWrapper)).toHaveLength(1);
+    expect(root.findAllByProps({'data-testid': 'banner-body'})).toHaveLength(1);
 
     renderer.act(() => {
       store.dispatch(addToast(secondNotificationMessage, {destination}));
     });
 
-    expect(root.findAllByType(BannerBodyWrapper)).toHaveLength(2);
+    expect(root.findAllByProps({'data-testid': 'banner-body'})).toHaveLength(2);
 
     const [firstNotification, secondNotification] = toastNotifications(store.getState());
 
     renderer.act(() => {
       const firstNotificationNode = root.findByProps({notification: firstNotification});
-      firstNotificationNode.findByType(CloseButton).props.onClick();
+      firstNotificationNode.findByProps({'aria-label': 'dismiss'}).props.onClick();
     });
 
     expect(dispatch).toHaveBeenCalledWith(dismissNotification(firstNotification));
-    expect(root.findAllByType(BannerBodyWrapper)).toHaveLength(1);
+    expect(root.findAllByProps({'data-testid': 'banner-body'})).toHaveLength(1);
 
     renderer.act(() => {
       const secondNotificationNode = root.findByProps({notification: secondNotification});
-      secondNotificationNode.findByType(CloseButton).props.onClick();
+      secondNotificationNode.findByProps({'aria-label': 'dismiss'}).props.onClick();
     });
 
     expect(dispatch).toHaveBeenCalledWith(dismissNotification(secondNotification));
-    expect(root.findAllByType(BannerBodyWrapper)).toHaveLength(0);
+    expect(root.findAllByProps({'data-testid': 'banner-body'})).toHaveLength(0);
   });
 
   it('sorts notification in descending order based on timestamp', () => {