single control flow for both Esc and Ctrl+C (#2691)

Esc and Ctrl+C while a task is running should do the same thing. There
were some cases where pressing Esc would leave a "stuck" widget in the
history; this fixes that and cleans up the logic so there's just one
path for interrupting the task. Also clean up some subtly mishandled key
events (e.g. Ctrl+D would quit the app while an approval modal was
showing if the textarea was empty).

---------

Co-authored-by: Ahmed Ibrahim <aibrahim@openai.com>

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

@@ -1,6 +1,7 @@
 use codex_core::protocol::TokenUsage;
 use crossterm::event::KeyCode;
 use crossterm::event::KeyEvent;
+use crossterm::event::KeyEventKind;
 use crossterm::event::KeyModifiers;
 use ratatui::buffer::Buffer;
 use ratatui::layout::Constraint;
@@ -657,6 +658,15 @@ impl ChatComposer {
     /// Handle key event when no popup is visible.
     fn handle_key_event_without_popup(&mut self, key_event: KeyEvent) -> (InputResult, bool) {
         match key_event {
+            KeyEvent {
+                code: KeyCode::Char('d'),
+                modifiers: crossterm::event::KeyModifiers::CONTROL,
+                kind: KeyEventKind::Press,
+                ..
+            } if self.is_empty() => {
+                self.app_event_tx.send(AppEvent::ExitRequest);
+                (InputResult::None, true)
+            }
             // -------------------------------------------------------------
             // History navigation (Up / Down) – only when the composer is not
             // empty or when the cursor is at the correct position, to avoid