Pin the memory label chip padding, not its retired background

The Tailwind 4 move (#2443) dropped the chip's bg-surface/80, which never rendered under Tailwind 3, so this branch's source pin failed after merging main. The model counts the chip's px-1 padding; pin that class alone.

frontend-modern/src/components/Workloads/__tests__/stackedMemoryBarModel.branchcov0724pm.test.ts

@@ -231,7 +231,7 @@ describe('stackedMemoryBarModel (branch coverage 0724pm)', () => {
     });
 
     it('counts the padding the label chip carries in StackedMemoryBar', () => {
-      expect(stackedMemoryBarSource).toContain('bg-surface/80 px-1 text-center');
+      expect(stackedMemoryBarSource).toContain('px-1 text-center');
     });
   });
 });