docs(comm): accept + document standby aggregators and deleted-site viewer behavior; fix aggregator e2e ctor call for new params (plan R2-02 T14)

src/ZB.MOM.WW.ScadaBridge.Communication/ISiteAlarmLiveCache.cs

@@ -11,9 +11,12 @@ namespace ZB.MOM.WW.ScadaBridge.Communication;
 /// reflects alarm transitions in near-real-time instead of re-polling every 15s.
 /// <para>
 /// <b>Hard constraint (locked <c>[PERM]</c>):</b> there is NO persisted central alarm
-/// store. This cache is purely in-memory and lives only on the active central node —
-/// no EF entity/table/migration backs it. On a NodeA↔NodeB failover the new active
-/// node re-seeds from scratch.
+/// store. This cache is purely in-memory, per-node — no EF entity/table/migration backs
+/// it. In routine operation only the active node (behind Traefik) hosts viewers, so only
+/// it runs aggregators; browsing the standby node directly (diagnostic ports) starts an
+/// independent read-only aggregator there — accepted (arch review 02 round 2, N8):
+/// bounded (one stream/site, viewer-capped), read-only, and torn down by the viewer
+/// linger. On a NodeA↔NodeB failover the new active node re-seeds from scratch.
 /// </para>
 /// <para>
 /// <b>Reference-counted lifecycle:</b> the first <see cref="Subscribe"/> for a site