feat(tui): add new designs experiment (#55818)

packages/tui/src/component/dialog-experiments.tsx

@@ -14,7 +14,13 @@ type Experiment = {
 // In-flight features anyone can opt into. Each entry is temporary: an
 // experiment either graduates (delete the entry, make the behavior
 // unconditional) or dies (delete the entry and the branch it gated).
-export const experiments: Experiment[] = []
+export const experiments: Experiment[] = [
+  {
+    id: "new-designs",
+    title: "New designs",
+    description: "Preview the new TUI designs",
+  },
+]
 
 export function DialogExperiments() {
   const config = useConfig()