Auto-archive previously wiped .fusion/tasks/{id}/ for stale done tasks
even while downstream agents (triage/todo/in-progress/in-review) still
needed to read those sibling specs from disk. Now the sweep skips any
done task that has an active dependent. The executor prompt also
instructs the agent to fall back to fn_task_show when sibling spec
files are missing on disk (e.g., manually archived deps).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
f57a692eeb