* feat(server): control Hub execution lifecycle
* fix(server): archive only execution-owned worktrees
* fix(server): serialize Hub execution control after create
* test(server): compare Hub worktree paths canonically
* fix(server): make absent Hub controls idempotent
A Hub can own an execution before agent creation materializes. Treating an absent daemon-scoped record as already stopped or archived lets finality complete without revealing or affecting another daemon's execution.