fix apply patch when only one file is rendered (#2468)

<img width="809" height="87" alt="image"
src="https://github.com/user-attachments/assets/6fe69643-10d7-4420-bbf2-e30c092b800f"
/>

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

@@ -695,7 +695,7 @@ fn apply_patch_request_shows_diff_summary() {
 
     // Per-file summary line should include the file path and counts
     assert!(
-        blob.contains("README.md (+2 -0)"),
+        blob.contains("README.md"),
         "missing per-file diff summary: {blob:?}"
     );
 }