Keep interrupted prompts in conversation history (#33198)

## What changed

- Leave an output-free interrupted prompt in the transcript and open a blank
  composer for the user's next instruction.
- Use the normal interruption notice for both `Esc` and `Ctrl-C` interrupts.
- Track safety-buffering prompts separately so failed retries can still restore
  the prompt, including after switching between threads.

## Testing

- Cover output-free `Esc` and `Ctrl-C` interrupts, failed safety-buffer retries,
  and restoration of safety-buffer state from thread snapshots.

GitOrigin-RevId: 30b368d00dfdb981d06d4c95ce3f252389b7917c

codex-rs/tui/src/chatwidget/tests/app_server.rs

@@ -190,6 +190,20 @@ async fn safety_buffering_remains_visible_until_turn_completes() {
     assert!(!render_bottom_popup(&chat, /*width*/ 80).contains(SAFETY_BUFFERING_HEADER_TEXT));
 }
 
+#[tokio::test]
+async fn failed_safety_buffering_retry_restores_submitted_prompt() {
+    let (mut chat, _rx, mut op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    start_safety_buffering_test_turn(&mut chat, &mut op_rx);
+
+    chat.prepare_safety_buffering_retry();
+    assert!(chat.input_queue.user_turn_pending_start);
+
+    chat.fail_safety_buffering_retry();
+
+    assert_eq!(chat.composer_text_with_pending(), "Explain the request");
+    assert!(!chat.input_queue.user_turn_pending_start);
+}
+
 #[tokio::test]
 async fn safety_buffering_without_retry_shows_short_app_message() {
     let (mut chat, _rx, mut op_rx) = make_chatwidget_manual(/*model_override*/ None).await;