Match pinned transcript headers to the original prompt style (#48775)

## What changed

Add the `› ` prefix to pinned prompt headers, using bold red for spoken prompts and bold dim styling for other prompts. Reserve one column when truncating the header.

## Testing

Add a rendering test comparing pinned headers with the original prompt rows for both regular and spoken prompts. Update snapshots for the prefix and display-width truncation.

GitOrigin-RevId: 89c2d9267374ef8f6504058c12c078025f302fef

codex-rs/tui/src/transcript_view/prompt_header.rs

@@ -46,8 +46,16 @@ pub(super) fn line(
         message
     };
     Some(truncate_line_with_ellipsis_if_overflow(
-        Line::from(message).style(crate::style::history_prompt_style()),
-        usize::from(width),
+        Line::from(vec![
+            if prompt.spoken {
+                "› ".red().bold()
+            } else {
+                "› ".bold().dim()
+            },
+            message.into(),
+        ])
+        .style(crate::style::history_prompt_style()),
+        usize::from(width.saturating_sub(1)),
     ))
 }
 

codex-rs/tui/src/transcript_view/prompt_header_tests.rs

@@ -1,6 +1,7 @@
 //! Sticky context follows the visible turn while leaving source text and hit rows intact.
 
 use super::*;
+use crate::history_cell::new_spoken_user_prompt;
 use crate::history_cell::new_user_prompt;
 use crate::transcript_view::tests::cell;
 use crate::transcript_view::tests::render;
@@ -84,6 +85,36 @@ fn header_sanitizes_controls_and_truncates_by_display_width() {
     insta::assert_snapshot!(line.to_string());
 }
 
+#[test]
+fn pinned_prompt_matches_the_original_prompt_style() {
+    for prompt in [
+        new_user_prompt("keep going".into(), Vec::new(), Vec::new(), Vec::new()),
+        new_spoken_user_prompt("keep going".into()),
+    ] {
+        let width = 30;
+        let mut expected = Buffer::empty(Rect::new(
+            /*x*/ 0, /*y*/ 0, width, /*height*/ 3,
+        ));
+        TextLayout::new(prompt.transcript_hyperlink_lines(width), width).render(
+            expected.area,
+            &mut expected,
+            /*start_row*/ 0,
+        );
+        let cells: Vec<Arc<dyn HistoryCell>> = vec![
+            Arc::new(prompt),
+            cell("one\ntwo\nthree\nfour\nfive\nsix\nseven\neight"),
+        ];
+        let mut view = TranscriptView::default();
+        let actual = render(&mut view, &cells, width, /*height*/ 7);
+
+        assert_eq!(
+            &actual.content[..usize::from(width)],
+            &expected.content[usize::from(width)..usize::from(width * 2)]
+        );
+        assert_eq!(view.area.y, 1);
+    }
+}
+
 #[test]
 fn mouse_selection_preserves_header_reservation_at_turn_boundaries() {
     let cells = vec![

codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__prompt_header__tests__header_sanitizes_controls_and_truncates_by_display_width.snap

@@ -1,6 +1,5 @@
 ---
 source: tui/src/transcript_view/prompt_header_tests.rs
-assertion_line: 76
 expression: line.to_string()
 ---
-界 café next ques…
+› 界 café next q…

codex-rs/tui/src/transcript_view/snapshots/codex_tui__transcript_view__prompt_header__tests__prompt_header_tracks_reading_and_yields_to_visible_prompts_and_short_screens.snap

@@ -4,21 +4,21 @@ assertion_line: 68
 expression: "snapshots.join(\"\\n\\n\")"
 ---
 Latest
-Second café question
+› Second café question
 seven
 eight
 nine
 ten
 
 Earlier answer
-First question
+› First question
 one
 two
 three
 four
 
 After prepend
-First question
+› First question
 one
 two
 three