feat(opencode): add observability logging to push relay and session status

Add structured logging to the push notification pipeline so events
can be traced end-to-end when --print-logs is enabled:
- push-relay map(): log every classification decision and skip reason
- push-relay dedupe(): log suppressed duplicates with elapsed time
- push-relay start()/stop(): log init failures and teardown
- session/status: log every idle/busy/retry transition