docs(#420): final reconciliation — alarms-over-gateway feature complete; C.1 superseded

#420 (filed 2026-05-01 as '4 inert scaffolds + D.1 smoke') is stale. Current
master + the mxaccessgw sibling repo show the feature landed on both sides:

- mxaccessgw A.2/A.4: native alarms served via the wnwrap consumer
  (WnWrapAlarmConsumer over WNWRAPCONSUMERLib.wwAlarmConsumerClass) +
  FailoverAlarmConsumer + AlarmDispatcher; StreamAlarms active-alarm snapshot
  (20 alarms verified live). The WM_APP-pump premise this issue was written
  against was ruled out by the 2026-05-01 probes; the design pivoted to wnwrap.
- mxaccessgw A.3: NotWiredAlarmRpcDispatcher gone (only in generated proto);
  ack routes MxGatewayClient.AcknowledgeAlarmAsync -> AlarmClient.AlarmAckByGUID.
- lmxopcua: GalaxyDriver : IAlarmSource wires GatewayGalaxyAlarmFeed
  (-> OnAlarmEvent, native metadata incl. operator-comment) + inbound ack via
  GatewayGalaxyAlarmAcknowledger; native feed live-proven by
  GatewayGalaxyAlarmFeedLiveTests.
- C.1 (SdkAlarmHistorianWriteBackend / aahClientManaged): SUPERSEDED. The whole
  Wonderware sidecar was retired; alarm-history writes cut over to the
  HistorianGateway (GatewayAlarmHistorianWriter, SendEvent path), live-verified
  2026-07-15 (R2-06/R2-08, 6/6). The target no longer exists in the tree.

Updated the alarms-over-gateway.md banner (final reconciliation) + the
alarms-d1-smoke-artifact.md status note. Sole residual = a Windows-parity-rig
running-server OPC UA A&C round-trip (needs live Galaxy + human IDE).

docs/plans/alarms-d1-smoke-artifact.md

@@ -1,7 +1,16 @@
 # Alarms D.1 — smoke artifact
 
-> **Status (2026-05-29): alarm-source leg VERIFIED. Historian-write leg still
-> pending the Windows sidecar + live AVEVA Historian.**
+> **Status (2026-05-29): alarm-source leg VERIFIED.** ~~Historian-write leg still
+> pending the Windows sidecar + live AVEVA Historian.~~
+>
+> ✅ **UPDATE 2026-07-15 (Gitea #420): the historian-write leg is no longer a
+> Wonderware-sidecar concern — it was cut over to the HistorianGateway.** Alarm
+> events now write through `GatewayAlarmHistorianWriter` (the gateway `SendEvent`
+> path behind `SqliteStoreAndForwardSink`), and alarm `SendEvent`→`ReadEvents`+ack
+> was **live-verified 2026-07-15** against the real AVEVA historian (R2-06/R2-08,
+> 6/6 green). The bespoke Wonderware sidecar + `SdkAlarmHistorianWriteBackend`
+> were retired. So this D.1 artifact's alarm-source leg is verified and the
+> write-back leg is superseded-and-verified via the gateway.
 >
 > **Re-confirmed 2026-05-31** against the same gateway (`http://10.100.0.48:5120`):
 > the Skip-gated live test passed again, pulling a native `Raise` transition