* Fix smart sort ranking of done agents by completion time
Completed entries stayed in the Done sort class indefinitely when
same-state writes refreshed updatedAt without moving stateStartedAt.
Introduce agentEntryCompletionAt() to use actual completion time for
both age display and sort eligibility, ensuring consistent aging
regardless of hook updates.
* Fix smart sort ranking of done agents by completion time
Co-authored-by: Orca <help@stably.ai>
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Co-authored-by: Orca <help@stably.ai>
