Allow naming sessions with /new and /clear (#34605)

## What changed

- Accept an optional session name after `/new` or `/clear`.
- Set the requested name through the app server when starting the new thread and update the attached session with that name.
- Report naming failures in the chat while still attaching the newly created thread.

## Testing

- Cover named `/new` and `/clear` dispatch, app-server name persistence, and the existing unnamed `/clear` behavior.

GitOrigin-RevId: 570886abb4af522123f0693ce05d2415e1c0d902

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

@@ -2104,7 +2104,39 @@ async fn slash_clear_requests_ui_clear_when_idle() {
 
     chat.dispatch_command(SlashCommand::Clear);
 
-    assert_matches!(rx.try_recv(), Ok(AppEvent::ClearUi));
+    assert_matches!(rx.try_recv(), Ok(AppEvent::ClearUi { name: None }));
+}
+
+#[tokio::test]
+async fn slash_new_with_name_requests_named_session() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    chat.bottom_pane
+        .set_composer_text("/new   Add User  ".to_string(), Vec::new(), Vec::new());
+
+    chat.handle_key_event(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
+
+    assert_matches!(
+        rx.try_recv(),
+        Ok(AppEvent::NewSession {
+            name: Some(name)
+        }) if name == "Add User"
+    );
+}
+
+#[tokio::test]
+async fn slash_clear_with_name_requests_named_session() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    chat.bottom_pane
+        .set_composer_text("/clear   Add User  ".to_string(), Vec::new(), Vec::new());
+
+    chat.handle_key_event(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
+
+    assert_matches!(
+        rx.try_recv(),
+        Ok(AppEvent::ClearUi {
+            name: Some(name)
+        }) if name == "Add User"
+    );
 }
 
 #[tokio::test]
@@ -2130,7 +2162,7 @@ async fn slash_clear_after_ctrl_c_keeps_stashed_draft_recallable() {
         .set_composer_text("/clear".to_string(), Vec::new(), Vec::new());
     chat.handle_key_event(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
 
-    assert_matches!(rx.try_recv(), Ok(AppEvent::ClearUi));
+    assert_matches!(rx.try_recv(), Ok(AppEvent::ClearUi { name: None }));
     chat.handle_key_event(KeyEvent::new(KeyCode::Up, KeyModifiers::NONE));
     assert_eq!(chat.bottom_pane.composer_text(), stashed_draft);