At 76%, molecule containers fail with "container is not running" because
overlay2 runs out of space under parallel DinD load. The gentle prune
(until=1h) at 75% was insufficient — runners stayed at 76% because
nothing was older than 1h on busy runners.
Lower the critical threshold to 75% so the full prune (no until filter)
triggers immediately when disk reaches the level where tests fail. Also
lower the gentle prune threshold to 70% to start cleanup earlier.
This matches the infra CI disk gate which skips tests at 75%+.
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
