tui: ^C in prompt area resets history navigation cursor (#5078)

^C resets the history navigation, similar to zsh/bash.

Fixes #4834

------
https://chatgpt.com/codex/tasks/task_i_68e9674b6ac8832c8212bff6cba75e87

codex-rs/tui/src/bottom_pane/mod.rs

@@ -236,7 +236,7 @@ impl BottomPane {
             CancellationEvent::NotHandled
         } else {
             self.view_stack.pop();
-            self.set_composer_text(String::new());
+            self.clear_composer_for_ctrl_c();
             self.show_ctrl_c_quit_hint();
             CancellationEvent::Handled
         }
@@ -270,6 +270,11 @@ impl BottomPane {
         self.request_redraw();
     }
 
+    pub(crate) fn clear_composer_for_ctrl_c(&mut self) {
+        self.composer.clear_for_ctrl_c();
+        self.request_redraw();
+    }
+
     /// Get the current composer text (for tests and programmatic checks).
     pub(crate) fn composer_text(&self) -> String {
         self.composer.current_text()