fix(opcua,drivers): carry driver status sub-codes to clients (#519) + health-write ordering (#517)

#519 — a driver's OPC UA status code now reaches a client with its sub-code intact.
DriverInstanceActor projected the driver's uint onto a 3-state Good/Uncertain/Bad enum
and OtOpcUaNodeManager re-expanded Bad to a bare 0x80000000, so BadNoCommunication,
BadTypeMismatch and BadNotSupported were indistinguishable on the wire and every
driver's status constants (incl. the 16 #497 had just corrected) were diagnostic in
logs only. Resolved by option (b): the raw uint rides AttributeValuePublished ->
AttributeValueUpdate -> IOpcUaAddressSpaceSink.WriteValue, OpcUaQuality is deleted, and
severity classification is a helper (OpcUaStatus.IsGood/IsUncertain/IsBad).

The surface was wider than the issue costed (41 files, not "the sink and 3
implementations"): OpcUaQuality had non-driver producers with no uint to carry.
Each got its natural code — BadInternalError for a failed virtual-tag script,
BadNoCommunication for driver comms loss — and ScriptedAlarmHostActor's pair of
mutually-inverse uint<->enum mappers is deleted, having round-tripped a code the
engine already held. AddressSpaceApplier's removal writes deliberately keep the
generic Bad: not losing a code the driver had is this issue; inventing one for the
deploy path is a separate call.

Behaviour change: WriteAlarmQuality fires its Part 9 event on a status-code change
rather than a severity-bucket change. While the annotation was 3-state those were the
same predicate; now a move between two Bad reasons changes what a subscriber reads.

New SDK-free named constants live on Commons.OpcUa.OpcUaStatus, and
StatusCodeParityTests is widened to cover them — that guard is reflection-driven, so
it can only see a named constant, never an inline literal.

#517 — the symptom is real but the issue named the wrong path and its fix was unsafe.
ShutdownAsync cannot race: DriverInstanceActor calls it from PostStop, after the
mailbox drains. (Core/Hosting/DriverHost, the one class with a concurrent GetHealth,
has no production call site.) InitializeAsync can: it runs on a fire-and-forget
Task.Run, and MTConnectDriver writes Healthy then starts loops that can throw into a
catch which disposes the client before writing Faulted.

Moving the write earlier, as suggested, inverts the terminal state — teardown drains
in-flight loops that write health as they unwind, so a late loop could leave Healthy at
rest with every connection closed. The fix is a bracket (conservative before, terminal
after), applied to MTConnect's init-failure path only; shutdown keeps its single
trailing write, and the rule plus the reachability table are documented on
IDriver.ShutdownAsync.

CalculationDriver.GetHealth returned a hard-coded Healthy that consulted nothing —
Healthy before initialize, after shutdown and after dispose. Now derived from _running.
Its test, named Health_is_always_Connected, asserted the defect and is replaced.

Every new guard was falsified by breaking the production code and watching it go red.
The two sub-code tests each assert two different Bad codes, since a single-code
assertion could pass against a hard-coded constant under the old projection.

Pre-existing failures, verified unchanged on a stashed tree and not chased: 4 in
Driver.AbLegacy.IntegrationTests (slc500/micrologix/plc5 fixtures not up) and 3 in
Host.IntegrationTests.

Closes #517
Closes #519

Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo

tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/DualNamespaceAddressSpaceTests.cs

@@ -65,8 +65,8 @@ public sealed class DualNamespaceAddressSpaceTests
             MaterialiseDualTree(sink);
             // One driver publish per NodeId (the fan-out the DriverHostActor performs) — identical payload.
             var ts = DateTime.UtcNow;
-            sink.WriteValue(RawTagPath, 42.5f, OpcUaQuality.Good, ts, AddressSpaceRealm.Raw);
-            sink.WriteValue(UnsVarPath, 42.5f, OpcUaQuality.Good, ts, AddressSpaceRealm.Uns);
+            sink.WriteValue(RawTagPath, 42.5f, OpcUaStatus.Good, ts, AddressSpaceRealm.Raw);
+            sink.WriteValue(UnsVarPath, 42.5f, OpcUaStatus.Good, ts, AddressSpaceRealm.Uns);
 
             using var session = await OpenSessionAsync($"opc.tcp://127.0.0.1:{port}/OtOpcUa", ct);
 
@@ -125,8 +125,8 @@ public sealed class DualNamespaceAddressSpaceTests
             // The single source (one RawPath) fans to the raw NodeId AND every referencing UNS NodeId with
             // identical value/quality/timestamp — the fan-out drift invariant.
             var ts = new DateTime(2026, 7, 16, 8, 30, 0, DateTimeKind.Utc);
-            sink.WriteValue(RawTagPath, 123.75f, OpcUaQuality.Good, ts, AddressSpaceRealm.Raw);
-            sink.WriteValue(UnsVarPath, 123.75f, OpcUaQuality.Good, ts, AddressSpaceRealm.Uns);
+            sink.WriteValue(RawTagPath, 123.75f, OpcUaStatus.Good, ts, AddressSpaceRealm.Raw);
+            sink.WriteValue(UnsVarPath, 123.75f, OpcUaStatus.Good, ts, AddressSpaceRealm.Uns);
 
             var rawValue = await session.ReadValueAsync(new NodeId(RawTagPath, rawNs), ct);
             var unsValue = await session.ReadValueAsync(new NodeId(UnsVarPath, unsNs), ct);