fix: focus After when opening a diff file

src/tui.rs

@@ -8675,6 +8675,7 @@ mod tests {
         let mut diff = diff_comparison(vec![deletion_file(), added]);
         diff.handle(Input::Down);
         diff.handle(Input::Enter);
+        diff.handle(Input::BackTab);
         for _ in 0..4 {
             diff.handle(Input::Right);
         }