- Add Towerops.TaskSupervisor to supervision tree, replace bare spawn/1
in agent channel with supervised tasks for polling data processing
- Change DiscoveryWorker from max_attempts: 1 to 3 with retryable error
classification (transient errors retry, permanent errors discard)
- Name all 9 parallel polling tasks and log timeouts/crashes instead of
silently dropping results via Stream.run()
- Add tests for TaskSupervisor presence and error classification
