@task_handler never built or passed cloud_logs_url, so every app using
it (incl. modelling_e2e) ran run_subtask with the None default and the
CloudWatch deep-link was never saved onto the SubTask. @subtask_handler
did this correctly.
Extract the URL builder into a shared utilities/aws_lambda/cloud_logs.py
(public cloudwatch_url()), use it from both handlers, and pass the URL
into run_subtask from @task_handler. Add regression tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
