feat(opcua): IOpcUaAddressSpaceSink.WriteStatuses — status-only batch write retaining the node value (03/S15)

archreview/plans/R3-02-stale-good-family-plan.md

@@ -651,3 +651,21 @@ test could only pass once the production change landed.
 - Docs: `docs/drivers/Mqtt.md` §"Quality on connection loss and re-subscribe" (links the contract in
   `DriverLifecycle.md`, records the two distinct "not communicating" codes and the operator-visible
   behaviour change).
+
+### T6 — `IOpcUaAddressSpaceSink.WriteStatuses` (interface default + node manager + both sinks)
+
+- RED (the guard, first): adding the member to the interface and running
+  `--filter "…DeferredSinkForwardingReflectionTests"` ⇒ **`Every_forwarding_interface_method_reaches_the_inner_sink`
+  FAILED**. Note the failure surfaced as `System.ArgumentNullException : Value cannot be null. (Parameter
+  'statuses')` rather than the guard's "did NOT forward" message — the reflection harness passes `null`
+  for an `IReadOnlyList<>` parameter, so the *interface default* ran on the wrapper and threw. Red for
+  the right reason (the member was not forwarded); green once `DeferredAddressSpaceSink.WriteStatuses`
+  forwards. This is the memory'd "Deferred sink doesn't forward the new member" trap, and here the
+  default is not merely slower — it writes a **null value**, erasing the very value the annotation exists
+  to keep.
+- RED (node manager): `--filter "…OtOpcUaNodeManagerWriteStatusesTests"` ⇒ **build failure**, `CS1061:
+  'OtOpcUaNodeManager' does not contain a definition for 'WriteStatuses'` (×5).
+- GREEN: 5/5 new; full `OpcUaServer.Tests` 495 passed / 1 skipped; `Commons.Tests` 348/348.
+- An unmaterialised NodeId is **skipped and not counted as a failure** (Debug tally via the SDK static
+  trace — the manager has no `ILogger`): the caller's per-driver index racing a surgical remove is an
+  expected shape, not a fault.

archreview/plans/R3-02-stale-good-family-plan.md.tasks.json

@@ -41,7 +41,7 @@
     {
       "id": "T6",
       "subject": "IOpcUaAddressSpaceSink.WriteStatuses (StatusWrite, default impl) + OtOpcUaNodeManager status-only batch retaining value + SdkAddressSpaceSink/DeferredAddressSpaceSink forwards (03/S15)",
-      "status": "pending",
+      "status": "done",
       "blockedBy": []
     },
     {