Suggest conversation-based thread titles in /rename (#40495)

## What changed

- Generate a title suggestion from the latest substantive user and assistant messages when the TUI `/rename` prompt opens.
- Prefill the prompt with the result while keeping it editable and preserving any text the user enters before generation finishes.
- Bound and escape the conversation context, omit commentary and IDE context, and correlate responses with the active thread and prompt so stale suggestions are ignored.

## Testing

- Cover conversation selection and prompt construction, generated-title delivery through the embedded app server, loading and prefilled prompt states, stale responses, and preservation of manual edits.

GitOrigin-RevId: 1e7f1d5d4f6503ff9da0548388f610c446c130ca

codex-rs/tui/src/app/event_dispatch.rs

@@ -2472,6 +2472,13 @@ impl App {
                     }
                 }
             }
+            AppEvent::SuggestThreadName {
+                thread_id,
+                request_id,
+            } => {
+                self.suggest_thread_name(app_server, thread_id, request_id)
+                    .await;
+            }
             AppEvent::ThreadTitleStarted {
                 thread_id,
                 destination,
@@ -2513,6 +2520,17 @@ impl App {
                             }
                         }
                     }
+                    ThreadTitleDestination::RenameSuggestion { request_id } => {
+                        let suggestion = result
+                            .ok()
+                            .and_then(|response| super::thread_title::parse_thread_title(&response));
+
+                        self.chat_widget.apply_thread_name_suggestion(
+                            thread_id,
+                            request_id,
+                            suggestion.as_deref(),
+                        );
+                    }
                 }
             }
             AppEvent::StopAgentsOverviewThread { thread_id } => {