test: add failing test for credits help icon in cloud user popover

Asserts that the help icon next to the credits balance renders as an
interactive button with the unified-credits tooltip text as its
accessible name. Today the icon is a bare <i> with v-tooltip and
cursor-help but no button semantics, so the tooltip is unreliable and
the icon is not focusable/clickable.

Refs FE-617

src/components/topbar/CurrentUserPopoverLegacy.test.ts

@@ -252,6 +252,20 @@ describe('CurrentUserPopoverLegacy', () => {
     expect(screen.getByText('Log Out')).toBeInTheDocument()
   })
 
+  describe('credits help icon (FE-617)', () => {
+    it('renders the credits help icon as an interactive button with the unified-credits tooltip as its accessible name', () => {
+      renderComponent()
+
+      const helpButton = screen.getByTestId('credits-info-button')
+      expect(helpButton).toBeInTheDocument()
+      expect(helpButton.tagName).toBe('BUTTON')
+      expect(helpButton).toHaveAttribute(
+        'aria-label',
+        enMessages.credits.unified.tooltip
+      )
+    })
+  })
+
   it('opens user settings and emits close event when settings item is clicked', async () => {
     const { user, onClose } = renderComponent()