restyle thinking outputs (#3755)

<img width="1205" height="930" alt="Screenshot 2025-09-16 at 2 23 18 PM"
src="https://github.com/user-attachments/assets/bb2494f1-dd59-4bc9-9c4e-740605c999fd"
/>

codex-rs/tui/src/markdown_stream.rs

@@ -333,11 +333,11 @@ mod tests {
         );
         for (i, l) in non_blank.iter().enumerate() {
             assert_eq!(
-                l.style.fg,
+                l.spans[0].style.fg,
                 Some(Color::Green),
                 "wrapped line {} should preserve green style, got {:?}",
                 i,
-                l.style.fg
+                l.spans[0].style.fg
             );
         }
     }