Normalize CRLF line endings in pasted text (#38704)

## Why

Replacing every carriage return with a line feed turns each CRLF pair into two
line breaks when text is pasted into the TUI composer.

## What changed

Normalize CRLF pairs before converting remaining bare carriage returns, so each
pasted line ending becomes a single line feed while existing line feeds remain
unchanged.

## Testing

Add a regression test covering mixed CRLF, bare CR, and LF line endings.

GitOrigin-RevId: 86c66d2a52fae52c9ae58c2f24a49eed685b60be

codex-rs/tui/src/app.rs

@@ -780,11 +780,12 @@ impl App {
                     self.handle_key_event(tui, app_server, key_event).await;
                 }
                 TuiEvent::Paste(pasted) => {
-                    // Many terminals convert newlines to \r when pasting (e.g., iTerm2),
-                    // but tui-textarea expects \n. Normalize CR to LF.
+                    // Pasted text may contain CRLF pairs or bare CRs (e.g., from iTerm2),
+                    // but tui-textarea expects LF. Normalize CRLF pairs before bare CRs so
+                    // each pasted line break becomes one LF and existing LFs stay unchanged.
                     // [tui-textarea]: https://github.com/rhysd/tui-textarea/blob/4d18622eeac13b309e0ff6a55a46ac6706da68cf/src/textarea.rs#L782-L783
                     // [iTerm2]: https://github.com/gnachman/iTerm2/blob/5d0c0d9f68523cbd0494dad5422998964a2ecd8d/sources/iTermPasteHelper.m#L206-L216
-                    let pasted = pasted.replace("\r", "\n");
+                    let pasted = pasted.replace("\r\n", "\n").replace('\r', "\n");
                     self.chat_widget.handle_paste(pasted);
                 }
                 TuiEvent::Draw | TuiEvent::Resume | TuiEvent::Resize(_) => {

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

@@ -153,6 +153,29 @@ fn test_absolute_path(path: &str) -> AbsolutePathBuf {
     AbsolutePathBuf::try_from(PathBuf::from(path)).expect("absolute test path")
 }
 
+#[tokio::test]
+async fn pasted_text_normalizes_mixed_line_endings_at_app_boundary() -> Result<()> {
+    let mut app = make_test_app().await;
+    let mut app_server = start_config_write_test_app_server(&app).await?;
+    let mut tui = crate::tui::test_support::make_test_tui()?;
+
+    app.handle_tui_event(
+        &mut tui,
+        &mut app_server,
+        TuiEvent::Paste("line1\r\nline2\rline3\nline4".to_string()),
+    )
+    .await?;
+
+    assert_snapshot!(app.chat_widget.composer_text_with_pending(), @r"
+    line1
+    line2
+    line3
+    line4
+    ");
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn chat_widget_frame_reuses_active_cell_height_across_frame_passes() {
     #[derive(Debug)]