refactor onboarding screen to a separate "app" (#2524)

this is in preparation for adding more separate "modes" to the tui, in
particular, a "transcript mode" to view a full history once #2316 lands.

1. split apart "tui events" from "app events".
2. remove onboarding-related events from AppEvent.
3. move several general drawing tools out of App and into a new Tui
class

codex-rs/tui/src/chatwidget/interrupts.rs

@@ -71,7 +71,7 @@ impl InterruptManager {
         self.queue.push_back(QueuedInterrupt::PatchEnd(ev));
     }
 
-    pub(crate) fn flush_all(&mut self, chat: &mut ChatWidget<'_>) {
+    pub(crate) fn flush_all(&mut self, chat: &mut ChatWidget) {
         while let Some(q) = self.queue.pop_front() {
             match q {
                 QueuedInterrupt::ExecApproval(id, ev) => chat.handle_exec_approval_now(id, ev),

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

@@ -104,14 +104,22 @@ async fn helpers_are_available_and_do_not_panic() {
     let tx = AppEventSender::new(tx_raw);
     let cfg = test_config();
     let conversation_manager = Arc::new(ConversationManager::default());
-    let mut w = ChatWidget::new(cfg, conversation_manager, tx, None, Vec::new(), false);
+    let mut w = ChatWidget::new(
+        cfg,
+        conversation_manager,
+        crate::tui::FrameRequester::test_dummy(),
+        tx,
+        None,
+        Vec::new(),
+        false,
+    );
     // Basic construction sanity.
     let _ = &mut w;
 }
 
 // --- Helpers for tests that need direct construction and event draining ---
 fn make_chatwidget_manual() -> (
-    ChatWidget<'static>,
+    ChatWidget,
     tokio::sync::mpsc::UnboundedReceiver<AppEvent>,
     tokio::sync::mpsc::UnboundedReceiver<Op>,
 ) {
@@ -121,6 +129,7 @@ fn make_chatwidget_manual() -> (
     let cfg = test_config();
     let bottom = BottomPane::new(BottomPaneParams {
         app_event_tx: app_event_tx.clone(),
+        frame_requester: crate::tui::FrameRequester::test_dummy(),
         has_input_focus: true,
         enhanced_keys_supported: false,
         placeholder_text: "Ask Codex to do anything".to_string(),
@@ -142,6 +151,7 @@ fn make_chatwidget_manual() -> (
         interrupts: InterruptManager::new(),
         needs_redraw: false,
         session_id: None,
+        frame_requester: crate::tui::FrameRequester::test_dummy(),
     };
     (widget, rx, op_rx)
 }