test(site-builder): parity harness neutralises documented editor-only differences (empty drop zone, empty-image placeholder)

Container marks the applied drop zone with data-wsb-dropzone.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

craft/src/components/layout/Container.dropZone.test.tsx

@@ -31,3 +31,11 @@ describe('Container empty-only drop zone', () => {
     expect(mount({ style: { minHeight: '100px' } }, false).style.minHeight).toBe('100px');
   });
 });
+
+describe('data-wsb-dropzone marker (harness hook)', () => {
+  test('set only while the drop-zone min-height is the one applied', () => {
+    expect(mount({ style: {} }, false).hasAttribute('data-wsb-dropzone')).toBe(true);
+    expect(mount({ style: {} }, true).hasAttribute('data-wsb-dropzone')).toBe(false);
+    expect(mount({ style: { minHeight: '100px' } }, false).hasAttribute('data-wsb-dropzone')).toBe(false);
+  });
+});

craft/src/components/layout/Container.tsx

@@ -117,6 +117,7 @@ export const Container: UserComponent<ContainerProps> = ({
       style: outerStyle,
       'data-craft-container': 'true',
       'data-fullwidth': fullWidth ? '' : undefined,
+      'data-wsb-dropzone': isEmpty && !style.minHeight ? '' : undefined,
       id: idValue,
       className: cssClass || undefined,
     },