Preserve transcript interaction when switching panes with arrow keys (#59472)

## Why

Directional pane switching cleared the parent conversation's transcript selection or Find state, so returning to it interrupted the interaction.

## What changed

Route left/right pane switches through the existing conversation toggle to park and restore each pane's transcript interaction. Explicitly focusing the main composer still clears transcript interaction.

## Testing

Extend the side-conversation test to cover restoring selections, Find text and caret position, and composer input after scrolling. Add a snapshot verifying that Find remains editable after switching away and back.

GitOrigin-RevId: 172f9be0df15517fbfe7f3773b63cbd1cef1cc77

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

@@ -40,12 +40,16 @@ impl App {
             && !on_child
             && (self.transcript_view.has_active_interaction()
                 || self.backtrack.overlay_preview_active);
-        let result = if main || (left && on_child) {
+        let result = if main {
             self.focus_main_composer(tui, app_server).await
-        } else if (sidebar || right)
+        } else if (left && on_child)
+            || (right && !on_child && child.is_some_and(|id| self.side_threads[&id].pane_open))
+        {
+            // Switching threads parks and restores each pane's transcript interaction.
+            self.toggle_side_conversation(tui, app_server).await
+        } else if sidebar
             && !on_child
             && let Some(child) = child
-            && (sidebar || self.side_threads[&child].pane_open)
         {
             let result = self.select_agent_thread(tui, app_server, child).await;
             if result.is_ok() && self.current_displayed_thread_id() == Some(child) {

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

@@ -3833,10 +3833,41 @@ async fn handle_start_side_seeds_navigation_before_thread_started() -> Result<()
         selected
     );
     app.transcript_view.end_select_mode();
-    // Ctrl-/ preserves interaction, so it exposes whether right actually cleaned up the parent.
-    keys!(toggle);
+    keys!(prefix, KeyCode::Left.into());
     assert_eq!(app.current_displayed_thread_id(), Some(parent_thread_id));
-    assert!(!app.transcript_view.has_active_interaction());
+    assert!(app.transcript_view.is_select_mode());
+    assert_eq!(
+        app.transcript_view.selected_text(&app.transcript_cells),
+        parent_text
+    );
+
+    keys!(prefix, main);
+    app.transcript_view.begin_search();
+    assert!(app.transcript_view.paste_search(parent_row));
+    keys!(KeyCode::Left.into());
+    let find = app.transcript_view.search_footer(size.width).unwrap();
+    keys!(prefix, KeyCode::Right.into());
+    keys!(prefix, KeyCode::Left.into());
+    assert_eq!(app.transcript_view.search_footer(size.width), Some(find));
+    keys!(KeyCode::Char('x').into());
+    let frame = side_frame(&mut app, &mut tui, size)?;
+    assert_app_snapshot!(
+        "direction_restores_parent_find",
+        frame.lines().find(|row| row.contains("Find:")).unwrap()
+    );
+
+    // Explicit composer focus ends Find. Scrolling alone keeps the composer active.
+    keys!(prefix, main);
+    read_side_history(&mut app, &mut tui, "parent")?;
+    keys!(prefix, KeyCode::Right.into());
+    keys!(prefix, KeyCode::Left.into());
+    assert!(side_frame(&mut app, &mut tui, size)?.contains(parent_row));
+    // End flushes the composer's pending paste-burst character.
+    keys!(KeyCode::Char('!').into(), KeyCode::End.into());
+    assert_eq!(
+        app.chat_widget.composer_text_with_pending(),
+        "parent draft-!"
+    );
     keys!(toggle);
 
     read_side_history(&mut app, &mut tui, "child")?;

codex-rs/tui/src/snapshots/codex_tui__app__tests__direction_restores_parent_find.snap

@@ -0,0 +1,5 @@
+---
+source: tui/src/app/tests.rs
+expression: "frame.lines().find(|row| row.contains(\"Find:\")).unwrap()"
+---
+  Find: parent-2x4                                            │   GPT-6.1-Sol default