Merge pull request 'docs: alarms-over-gateway plan banner — record A.2 dev-rig finding' (#418) from track-d1-followup-plan-banner into master

docs/plans/alarms-over-gateway.md

@@ -1,16 +1,32 @@
 # Plan — alarms over the mxaccessgw gateway
 
-> ✅ **Completed 2026-04-30 — historical record.**
-> The 14-PR sequence (A.1 / A.3, B.1 / B.2 / B.3 / B.4, C.1 / C.2,
-> E.1 / E.2 / E.3 / E.4 / E.5 / E.6 / E.7) shipped. The gateway-side
-> public RPC surface, the driver-native ack path, the sidecar alarm
-> historian writer, and the five client SDKs are all live. **A.2**
-> (worker MxAccess alarm subscription) and **A.4** (worker
-> ConditionRefresh command) require the AVEVA worker host's MxAccess
-> Toolkit C++ SDK and ship as a follow-up gated on dev-rig
-> validation. **D.1** (refresh `C:\publish` + smoke-run on the dev
-> rig) ships once A.2 is hardware-verified. The remainder of this
-> document is preserved as the design record.
+> ✅ **All 19 PRs merged 2026-04-30 — historical record.**
+> A.1 / A.2 / A.3 / A.4 (gateway proto + handlers + worker scaffold),
+> B.1 / B.2 / B.3 / B.4 / B.5 (driver, server, docs), C.1 / C.2
+> (sidecar alarm historian writer), D.1 (deploy script),
+> E.1 / E.2 / E.3 / E.4 / E.5 / E.6 / E.7 (5 client SDKs + lmxopcua
+> client surface). Public contract surface is live; client SDKs ship
+> the new RPCs; the sub-attribute fallback path keeps Galaxy alarms
+> functional today.
+>
+> ⚠️ **Worker-side native alarm subscription blocked on a dev-rig
+> finding (2026-04-30):** the MXAccess COM Toolkit at
+> `C:\Program Files (x86)\ArchestrA\Framework\Bin\ArchestrA.MXAccess.dll`
+> exposes no alarm-event family — only `OnDataChange`,
+> `OnWriteComplete`, `OperationComplete`, `OnBufferedDataChange`.
+> AVEVA's `aaAlarmManagedClient` / `ArchestrAAlarmsAndEvents.SDK`
+> assemblies are x64-only and incompatible with the worker's x86
+> bitness. **Operator decision needed before
+> `MX_EVENT_FAMILY_ON_ALARM_TRANSITION` carries any events:** either
+> accept the value-driven sub-attribute path as the production
+> architecture (operator-comment fidelity is the only v1 regression)
+> or add an x64 alarm-helper sub-process alongside the worker. See
+> `src/MxGateway.Worker/MxAccess/MxAccessAlarmEventSink.cs` in the
+> mxaccessgw repo for the architectural notes. Live
+> `aahClientManaged` alarm-event write call site
+> (`SdkAlarmHistorianWriteBackend` placeholder from PR C.1) and the
+> D.1 smoke artifact ship once those decisions resolve. The
+> remainder of this document is preserved as the design record.
 
 Coordinated epic across two repos: