Implement redraw debounce (#1599)

## Summary
- debouce redraw events so repeated requests don't overwhelm the
terminal
- add `RequestRedraw` event and schedule redraws after 100ms

## Testing
- `cargo clippy --tests`
- `cargo test` *(fails: Sandbox Denied errors in landlock tests)*

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https://chatgpt.com/codex/tasks/task_i_68792a65b8b483218ec90a8f68746cd8

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Co-authored-by: Michael Bolin <mbolin@openai.com>

codex-rs/tui/src/status_indicator_widget.rs

@@ -65,7 +65,7 @@ impl StatusIndicatorWidget {
                     std::thread::sleep(Duration::from_millis(200));
                     counter = counter.wrapping_add(1);
                     frame_idx_clone.store(counter, Ordering::Relaxed);
-                    app_event_tx_clone.send(AppEvent::Redraw);
+                    app_event_tx_clone.send(AppEvent::RequestRedraw);
                 }
             });
         }