Fix frontend test (#2247)

UI fixtures are brittle! Who knew.

codex-rs/tui/src/chatwidget/tests.rs

@@ -671,7 +671,10 @@ fn plan_update_renders_history_cell() {
     let cells = drain_insert_history(&rx);
     assert!(!cells.is_empty(), "expected plan update cell to be sent");
     let blob = lines_to_single_string(cells.last().unwrap());
-    assert!(blob.contains("Updated"), "missing plan header: {blob:?}");
+    assert!(
+        blob.contains("Update plan"),
+        "missing plan header: {blob:?}"
+    );
     assert!(blob.contains("Explore codebase"));
     assert!(blob.contains("Implement feature"));
     assert!(blob.contains("Write tests"));