Reopening an archived agent previously dead-ended at "workspace not
found": the agent record was un-archived but its workspace stayed
archived and was never sent to the client.
The daemon now un-archives the owning workspace alongside the agent when
its backing directory still exists, and the app auto-fires the restore
ahead of the missing-workspace gate so the user lands back in the
workspace rather than a dead end.
Worktrees whose directory was deleted on archive are not yet restorable
(recreating them from their branch is a follow-up); the workspace record
now persists its base branch as groundwork for that.