Revert "Streaming markdown (#1920)" (#1981)

This reverts commit 2b7139859e.

codex-rs/tui/src/app.rs

@@ -64,9 +64,6 @@ pub(crate) struct App<'a> {
     pending_history_lines: Vec<Line<'static>>,
 
     enhanced_keys_supported: bool,
-
-    /// Controls the animation thread that sends CommitTick events.
-    commit_anim_running: Arc<AtomicBool>,
 }
 
 /// Aggregate parameters needed to create a `ChatWidget`, as creation may be
@@ -176,7 +173,6 @@ impl App<'_> {
             file_search,
             pending_redraw,
             enhanced_keys_supported,
-            commit_anim_running: Arc::new(AtomicBool::new(false)),
         }
     }
 
@@ -193,7 +189,7 @@ impl App<'_> {
         // redraw is already pending so we can return early.
         if self
             .pending_redraw
-            .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
+            .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
             .is_err()
         {
             return;
@@ -204,7 +200,7 @@ impl App<'_> {
         thread::spawn(move || {
             thread::sleep(REDRAW_DEBOUNCE);
             tx.send(AppEvent::Redraw);
-            pending_redraw.store(false, Ordering::Release);
+            pending_redraw.store(false, Ordering::SeqCst);
         });
     }
 
@@ -225,30 +221,6 @@ impl App<'_> {
                 AppEvent::Redraw => {
                     std::io::stdout().sync_update(|_| self.draw_next_frame(terminal))??;
                 }
-                AppEvent::StartCommitAnimation => {
-                    if self
-                        .commit_anim_running
-                        .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
-                        .is_ok()
-                    {
-                        let tx = self.app_event_tx.clone();
-                        let running = self.commit_anim_running.clone();
-                        thread::spawn(move || {
-                            while running.load(Ordering::Relaxed) {
-                                thread::sleep(Duration::from_millis(50));
-                                tx.send(AppEvent::CommitTick);
-                            }
-                        });
-                    }
-                }
-                AppEvent::StopCommitAnimation => {
-                    self.commit_anim_running.store(false, Ordering::Release);
-                }
-                AppEvent::CommitTick => {
-                    if let AppState::Chat { widget } = &mut self.app_state {
-                        widget.on_commit_tick();
-                    }
-                }
                 AppEvent::KeyEvent(key_event) => {
                     match key_event {
                         KeyEvent {