docs: alarms-over-gateway completion banner + AlarmTracking v2 (PR B.5)

Sixteenth PR of the alarms-over-gateway epic
(docs/plans/alarms-over-gateway.md). Closes the documentation sweep
the plan calls for.

- docs/AlarmTracking.md — promoted top-level v2-final architecture
  doc (was a worktree-only draft pre-epic). Covers the three alarm
  sources (Galaxy MxAccess driver-native / Galaxy sub-attribute
  fallback / scripted alarms), how they converge on
  AlarmConditionService, the Acknowledge routing decision in
  DriverNodeManager (driver-native preferred over IWritable
  sub-attribute fallback), the sidecar historian write-back path
  for non-Galaxy producers, and cross-references to the plan +
  v1 archive.
- docs/v1/AlarmTracking.md — banner pointing readers at the v2
  doc; preserved as historical record.
- docs/drivers/Galaxy.md — capability list updated to include
  IAlarmSource (now eight capabilities, restored by B.2). Replaced
  the "IAlarmSource retired in 7.2" sentence with the restoration
  note + cross-link to docs/AlarmTracking.md.
- docs/plans/alarms-over-gateway.md — completion banner at the
  top of the plan, marking 14 of 16 PRs shipped 2026-04-30 and
  noting that A.2 + A.4 + D.1 are the hardware-gated follow-up.

Memory entries updated separately:
- project_alarms_over_gateway_epic.md (new) — epic summary +
  per-PR digest.
- project_galaxy_via_mxgateway.md — added "Alarms restored"
  bullet pointing at the new architecture.
- project_server_history_alarm_subsystems.md — bullet 2 updated
  to describe the new ack-routing decision (B.3) + bullet 3
  added describing the historian write-back path that B.4 + C.1
  + C.2 light up.
- MEMORY.md index — new pointer entry.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/plans/alarms-over-gateway.md

@@ -1,5 +1,17 @@
 # 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.
+
 Coordinated epic across two repos:
 
 - **`lmxopcua`** (this repo) — `c:\Users\dohertj2\Desktop\lmxopcua\`