send context window with task started (#2752)

- Send context window with task started
- Accounting for changing the model per turn

codex-rs/tui/src/chatwidget.rs

@@ -938,7 +938,7 @@ impl ChatWidget {
                 self.on_agent_reasoning_final()
             }
             EventMsg::AgentReasoningSectionBreak(_) => self.on_reasoning_section_break(),
-            EventMsg::TaskStarted => self.on_task_started(),
+            EventMsg::TaskStarted(_) => self.on_task_started(),
             EventMsg::TaskComplete(TaskCompleteEvent { .. }) => self.on_task_complete(),
             EventMsg::TokenCount(token_usage) => self.on_token_count(token_usage),
             EventMsg::Error(ErrorEvent { message }) => self.on_error(message),