When the liveness watcher finds the tmux session gone, it now settles
the worktree through the same probe_worktree/record_retention helpers
the kill uses: pristine trees are removed, anything else is retained as
exited-with-unsaved-work before anything is torn down. The dead session
drops its worktree reference once settled, so dismissing it neither
refuses nor retains twice. If the probe or store write fails, nothing
is destroyed and the tree stays attached to the record.
WORKTREES.md: written down the settle-then-drop and nothing-destroyed-
when-unrecordable rules alongside the existing exit rule.
Miguel Palhas
2fc19a886e