feat: include latest build id in task responses (#20181)

Adding the latest build ID is necessary to locate the logs associated
with the tasks in the UI.

cli/exp_task_status_test.go

@@ -193,6 +193,7 @@ STATE CHANGED  STATUS   HEALTHY  STATE  MESSAGE
   "workspace_agent_id": null,
   "workspace_agent_lifecycle": null,
   "workspace_agent_health": null,
+  "latest_build_id": null,
   "initial_prompt": "",
   "status": "running",
   "current_state": {