hint for codex resume on tui exit (#3757)

<img width="931" height="438" alt="Screenshot 2025-09-16 at 4 25 19 PM"
src="https://github.com/user-attachments/assets/ccfb8df1-feaf-45b4-8f7f-56100de916d5"
/>

codex-rs/tui/src/app.rs

@@ -15,6 +15,7 @@ use codex_core::config::persist_model_selection;
 use codex_core::model_family::find_family_for_model;
 use codex_core::protocol::TokenUsage;
 use codex_core::protocol_config_types::ReasoningEffort as ReasoningEffortConfig;
+use codex_protocol::mcp_protocol::ConversationId;
 use color_eyre::eyre::Result;
 use color_eyre::eyre::WrapErr;
 use crossterm::event::KeyCode;
@@ -33,6 +34,12 @@ use tokio::select;
 use tokio::sync::mpsc::unbounded_channel;
 // use uuid::Uuid;
 
+#[derive(Debug, Clone)]
+pub struct AppExitInfo {
+    pub token_usage: TokenUsage,
+    pub conversation_id: Option<ConversationId>,
+}
+
 pub(crate) struct App {
     pub(crate) server: Arc<ConversationManager>,
     pub(crate) app_event_tx: AppEventSender,
@@ -70,7 +77,7 @@ impl App {
         initial_prompt: Option<String>,
         initial_images: Vec<PathBuf>,
         resume_selection: ResumeSelection,
-    ) -> Result<TokenUsage> {
+    ) -> Result<AppExitInfo> {
         use tokio_stream::StreamExt;
         let (app_event_tx, mut app_event_rx) = unbounded_channel();
         let app_event_tx = AppEventSender::new(app_event_tx);
@@ -153,7 +160,10 @@ impl App {
             }
         } {}
         tui.terminal.clear()?;
-        Ok(app.token_usage())
+        Ok(AppExitInfo {
+            token_usage: app.token_usage(),
+            conversation_id: app.chat_widget.conversation_id(),
+        })
     }
 
     pub(crate) async fn handle_tui_event(