Step status and output lines arrive on two separate Progress<T> channels, so a
trailing "Running" line-message could be delivered after a step's terminal
Done/Failed and downgrade the badge back to orange. Guard against that
downgrade. Also reset each step's messages/status/expansion at the start of a
run so re-running no longer appends to the previous run's output.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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