fix(confirmations): add Pure Black border to AdvancedEIP1559Modal

Apply muted border on elevated surface in Pure Black dark mode and extend
styles tests to cover border gating alongside gas-fee-token-modal.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: georgewrmarshall

app/components/Views/confirmations/components/modals/advanced-eip1559-modal/advanced-eip1559-modal.styles.test.ts

@@ -3,7 +3,12 @@ import { AppThemeKey, Theme } from '../../../../../../util/theme/models';
 
 const MOCK_ELEVATED_SURFACE_COLOR = 'mock-elevated-surface-color';
 
+let mockIsPureBlackEnabled = false;
+
 jest.mock('../../../../../../util/theme/themeUtils', () => ({
+  get isPureBlackEnabled() {
+    return mockIsPureBlackEnabled;
+  },
   getElevatedSurfaceColor: jest.fn(() => MOCK_ELEVATED_SURFACE_COLOR),
 }));
 
@@ -18,11 +23,37 @@ const darkThemeModel: Theme = {
 };
 
 describe('advanced-eip1559-modal.styles', () => {
+  beforeEach(() => {
+    mockIsPureBlackEnabled = false;
+  });
+
   it('uses elevated surface color for the modal container', () => {
     const styles = styleSheet({
       theme: darkThemeModel,
     });
 
     expect(styles.container.backgroundColor).toBe(MOCK_ELEVATED_SURFACE_COLOR);
   });
+
+  it('does not apply muted border when pure black preview is off', () => {
+    const styles = styleSheet({
+      theme: darkThemeModel,
+    });
+
+    expect(styles.container.borderWidth).toBe(0);
+    expect(styles.container.borderColor).toBeUndefined();
+  });
+
+  it('applies muted border in pure black dark mode', () => {
+    mockIsPureBlackEnabled = true;
+
+    const styles = styleSheet({
+      theme: darkThemeModel,
+    });
+
+    expect(styles.container.borderWidth).toBe(1);
+    expect(styles.container.borderColor).toBe(
+      darkThemeModel.colors.border.muted,
+    );
+  });
 });

app/components/Views/confirmations/components/modals/advanced-eip1559-modal/advanced-eip1559-modal.styles.ts

@@ -1,13 +1,23 @@
 import { StyleSheet } from 'react-native';
-import { Theme } from '../../../../../../util/theme/models';
-import { getElevatedSurfaceColor } from '../../../../../../util/theme/themeUtils';
+import { AppThemeKey, Theme } from '../../../../../../util/theme/models';
+import {
+  getElevatedSurfaceColor,
+  isPureBlackEnabled,
+} from '../../../../../../util/theme/themeUtils';
 
 const styleSheet = (params: { theme: Theme }) => {
   const { theme } = params;
+  const { colors } = theme;
+  const isPureBlackDark =
+    isPureBlackEnabled && theme.themeAppearance === AppThemeKey.dark;
 
   return StyleSheet.create({
+    // TODO(Pure Black): Remove once MMDS ships pure-black-aware surface tokens.
+    // Drop getElevatedSurfaceColor, isPureBlackEnabled, and AppThemeKey checks.
     container: {
       backgroundColor: getElevatedSurfaceColor(theme),
+      borderWidth: isPureBlackDark ? 1 : 0,
+      borderColor: isPureBlackDark ? colors.border.muted : undefined,
       padding: 16,
       paddingBottom: 36,
       borderTopRightRadius: 16,