Harden flaky workflow tests

[tconley1428]

Summary

• remove the build-id test race by gating the worker transition with an explicit signal
• relax the logger sandbox workflow timeout so the test checks behavior instead of host speed

Testing

• uv run -m pytest tests/worker/test_workflow.py -k 'test_workflow_current_build_id_appropriately_set or test_disable_logger_sandbox' -q -n 0