Path-based NodeIds — decouple client contract from driver address

The pre-refactor design minted OPC UA NodeIds directly from the driver's
FullReference (the native-address string). That had three long-term
problems:

1. OPC UA Part 3 §5.2.2 requires NodeIds to be immutable across a node's
   lifetime. A rename of the underlying device address — Galaxy attribute,
   S7 tag, Modbus register alias — changed the NodeId and broke every
   client that had pinned the previous identifier.
2. Two drivers with coincidentally-matching native addresses (e.g. `temp`
   in Modbus and `temp` in S7 under different Equipment rows) collided on
   the NodeId identifier.
3. TagConfig was being placed verbatim on the wire; for drivers whose
   TagConfig is JSON (every driver shipped today, per the
   CK_Tag_TagConfig_IsJson check constraint), clients saw the raw JSON
   blob as the NodeId string.

Refactor:

* DriverNodeManager.Variable now mints a stable path-based NodeId
  `{driverId}/{folder-path}/{browseName}` and records the driver-side
  FullReference in a new _fullRefByNodeId map. OnReadValue / OnWriteValue
  / ResolveFullRef look the FullReference up via that map instead of
  casting NodeId.Identifier. The old cast path is preserved as a
  fallback so any test fixture that still registers variables with
  FullRef-shaped NodeIds keeps working.

* EquipmentNodeWalker.AddTagVariable now extracts the cross-driver
  `FullName` field from Tag.TagConfig before handing the address to
  DriverAttributeInfo. Every shipped driver stores the wire reference in
  TagConfig[FullName]; falling back to the raw string covers any future
  driver that wants an opaque non-JSON address. ExtractFullName is
  exposed internal for unit coverage.

* scripts/e2e/test-galaxy.ps1 defaults updated to the new path-based
  NodeIds. Verified live against p7-smoke-galaxy on the dev box:
  `ns=2;s=p7-smoke-galaxy/lab-floor/galaxy-line/reactor-1/Source` reads
  return Status=0x00000000 with a real Galaxy byte-array value.

Test suite: 195/195 Core.Tests + 283/283 Server.Tests green. Five new
ExtractFullName / FullName-passthrough tests added.

Task #112 GA-3 — golden-path read verified end-to-end; remaining E2E
script stages still blocked on pre-existing issues (ScriptedAlarm
predicate NRE on empty upstream cache, PowerShell $changeLines.Count
guard), tracked separately.
Task #134 — complete.

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

src/ZB.MOM.WW.OtOpcUa.Core/OpcUa/EquipmentNodeWalker.cs

@@ -1,3 +1,4 @@
+using System.Text.Json;
 using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 
@@ -157,7 +158,7 @@ public static class EquipmentNodeWalker
     private static void AddTagVariable(IAddressSpaceBuilder equipmentBuilder, Tag tag)
     {
         var attr = new DriverAttributeInfo(
-            FullName: tag.TagConfig,
+            FullName: ExtractFullName(tag.TagConfig),
             DriverDataType: ParseDriverDataType(tag.DataType),
             IsArray: false,
             ArrayDim: null,
@@ -166,6 +167,38 @@ public static class EquipmentNodeWalker
         equipmentBuilder.Variable(tag.Name, tag.Name, attr);
     }
 
+    /// <summary>
+    ///     Cross-driver TagConfig convention — the Config DB's <c>CK_Tag_TagConfig_IsJson</c>
+    ///     check constraint requires TagConfig to be a JSON object, and every shipped driver
+    ///     (Galaxy / Modbus / AB CIP / S7 / FOCAS / TwinCAT / ABLegacy) stores the wire-level
+    ///     address in a top-level <c>FullName</c> field. Extracting it here keeps the walker
+    ///     driver-agnostic while giving the driver the plain address string its backend
+    ///     expects at read-time — the raw JSON would otherwise be passed verbatim to
+    ///     <c>IReadable.ReadAsync</c> and the driver would fail to resolve the tag.
+    /// </summary>
+    /// <remarks>
+    ///     Falls back to the raw <paramref name="tagConfig"/> if it doesn't parse as JSON or
+    ///     the <c>FullName</c> field is absent. This preserves the pre-refactor behaviour for
+    ///     any legacy row that slipped past the check constraint or any future driver that
+    ///     wants an opaque non-JSON reference.
+    /// </remarks>
+    internal static string ExtractFullName(string tagConfig)
+    {
+        if (string.IsNullOrWhiteSpace(tagConfig)) return tagConfig;
+        try
+        {
+            using var doc = JsonDocument.Parse(tagConfig);
+            if (doc.RootElement.ValueKind == JsonValueKind.Object
+                && doc.RootElement.TryGetProperty("FullName", out var fullName)
+                && fullName.ValueKind == JsonValueKind.String)
+            {
+                return fullName.GetString() ?? tagConfig;
+            }
+        }
+        catch (JsonException) { /* fall through */ }
+        return tagConfig;
+    }
+
     /// <summary>
     ///     Parse <see cref="Tag.DataType"/> (stored as the <see cref="DriverDataType"/> enum
     ///     name string, decision #138) into the enum value. Unknown names fall back to