test(app-shell): assert the nesting error before the DOM shape in the package-sheet pin

So a regression's first failure shows React's own nesting error.

Claude-Session: https://claude.ai/code/session_01DrKzdPdyLLBW3qpZ4vtk7z
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/app-shell/src/views/metadata-admin/PackagesPage.pendingHeaderMarkup-11804.test.tsx

@@ -90,10 +90,10 @@ describe('PackageDetailSheet — the pending-changes header is valid markup (obj
     const header = await screen.findByText('Pending changes');
     // The count badge still sits inside the header, beside its label.
     expect(header.textContent).toBe(`Pending changes${drafts.length}`);
-    expect(header.tagName).not.toBe('P');
 
-    expect(paragraphsHoldingBlocks()).toEqual([]);
     expect(errors.filter((e) => NESTING.test(e))).toEqual([]);
+    expect(paragraphsHoldingBlocks()).toEqual([]);
+    expect(header.tagName).not.toBe('P');
   });
 
   it('a package with no drafts renders no header and logs no nesting error', async () => {