- Reconcile retries of a failing alarm subscribe back off (skip 2^(n-1)-1
ticks, cap 7 => >= every 4 min at the 30 s tick) so a hanging subscribe
cannot hold the mailbox every tick; the stack is logged once per streak.
- The unreachable handler re-attach logs at Warning (it only fires on a
regression).
- OpcUaClient: a failed SubscribeAlarmsAsync detaches its notification
handler and bounds the session cleanup to 5 s under _gate;
OnEventNotification drops events from subscriptions not registered in
_alarmSubscriptions, so a stray that survives cleanup cannot deliver.
- The retry test also covers 3 failures (crosses the backoff); its tick
positive control documents its dependence on the stub's changing health.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
Joseph Doherty
28ca04e466