Confirm the nuke prompt in the nuke_working_tree demo

The recording of this demo stops with the confirmation popup still on
screen. The explosion animation and the emptied Files panel that the demo
exists to show never happen at all. Nuking the working tree has asked for
confirmation since 238fdd573c, and the demo only selects the menu item, so
the nuke never runs. The demo asserted nothing about the outcome, so it
stayed green all the while.

Answer the confirmation, and assert that the Files panel ends up empty.
That assertion also holds the recording open until the animation has
played out and the panel has been refreshed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/integration/tests/demo/nuke_working_tree.go

@@ -39,6 +39,15 @@ var NukeWorkingTree = NewIntegrationTest(NewIntegrationTestArgs{
 					Title(Equals("")).
 					Select(Contains("Nuke working tree")).
 					Confirm()
-			})
+
+				t.ExpectPopup().Confirmation().
+					Title(Equals("Nuke working tree")).
+					Content(AnyString()).
+					Wait(1000).
+					Confirm()
+			}).
+			// Retries until the explosion animation has played out and the panel has
+			// been refreshed, so that the recording shows both.
+			IsEmpty()
 	},
 })