fix terminal corruption that could happen when onboarding and update banner (#5269)

Instead of printing characters before booting the app, make the upgrade
banner a history cell so it's well-behaved.

<img width="771" height="586" alt="Screenshot 2025-10-16 at 4 20 51 PM"
src="https://github.com/user-attachments/assets/90629d47-2c3d-4970-a826-283795ab34e5"
/>

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Co-authored-by: Josh McKinney <joshka@openai.com>

codex-rs/tui/src/update_prompt.rs

@@ -1,6 +1,5 @@
 #![cfg(not(debug_assertions))]
 
-use crate::UpdateAction;
 use crate::history_cell::padded_emoji;
 use crate::key_hint;
 use crate::render::Insets;
@@ -12,6 +11,7 @@ use crate::tui::FrameRequester;
 use crate::tui::Tui;
 use crate::tui::TuiEvent;
 use crate::updates;
+use crate::updates::UpdateAction;
 use codex_core::config::Config;
 use color_eyre::Result;
 use crossterm::event::KeyCode;
@@ -39,7 +39,7 @@ pub(crate) async fn run_update_prompt_if_needed(
     let Some(latest_version) = updates::get_upgrade_version_for_popup(config) else {
         return Ok(UpdatePromptOutcome::Continue);
     };
-    let Some(update_action) = crate::get_update_action() else {
+    let Some(update_action) = crate::updates::get_update_action() else {
         return Ok(UpdatePromptOutcome::Continue);
     };