test: wait for settings before appearance assertions

The Linux CI run could query the Appearance tab before the lazy Settings route finished loading. Appearance tests now wait for the Settings heading before interacting with its tabs, matching the stable navigation pattern used elsewhere.

src/renderer/src/App.test.tsx

@@ -1892,8 +1892,9 @@ describe('App', () => {
         name: /本地工作区/u
       })
     )
+    await screen.findByRole('heading', { name: '设置中心' })
     fireEvent.click(
-      await screen.findByRole('tab', { name: '外观' })
+      screen.getByRole('tab', { name: '外观' })
     )
     fireEvent.change(screen.getByLabelText('品牌名称'), {
       target: { value: '研发伙伴' }
@@ -2179,8 +2180,9 @@ describe('App', () => {
           name: /本地工作区/u
         })
       )
+      await screen.findByRole('heading', { name: '设置中心' })
       fireEvent.click(
-        await screen.findByRole('tab', { name: '外观' })
+        screen.getByRole('tab', { name: '外观' })
       )
       const projectsList = vi.mocked(api.projects.list)
       const expertsList = vi.mocked(api.experts.list)
@@ -5747,6 +5749,7 @@ describe('App', () => {
     render(<App />)
 
     fireEvent.click(await screen.findByText('本地工作区'))
+    await screen.findByRole('heading', { name: '设置中心' })
     fireEvent.click(screen.getByRole('tab', { name: '外观' }))
     fireEvent.click(screen.getByRole('radio', { name: /暗色/u }))