fix(opcua): Part 9 condition children get instance-scoped NodeIds (#629)

Create(assignNodeIds: true) asked CustomNodeManager2.New, whose default returns the
node's current id, so every condition child kept the type's ns=0 instance-declaration id
(or an SDK-generated ns=0 number): translate of a child path returned BadNoMatch and a
Read of a browsed child id was BadNodeIdUnknown or served from the TYPE (UnshelveTime 0
on a condition timed-shelved for a minute), bypassing the data-plane ACL.

OtOpcUaNodeManager.New now derives {conditionId}/{browsePath} in the condition's
namespace, so the ACL scope of a child is its condition's scope plus the path. The
ShelvingState methods adopt their original AlarmConditionType_ShelvingState_* id as
MethodDeclarationId so clients calling them by that id still resolve. Condition removal
and rebuild forget the whole PredefinedNodes subtree so a removed condition's children
stop answering.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

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

@@ -369,9 +369,8 @@ public sealed class ConditionMethodEventTests
     ///     Gitea #597: both paths applied the shelve with <c>shelvingTime 0</c>, which the SDK reads as "the
     ///     longest shelve allowed" — <c>MaxTimeShelved</c>, <c>int.MaxValue</c> ms — so every timed shelve
     ///     advertised ~24.8 days remaining while the engine expired it on time. Read through the event select
-    ///     clause rather than a Read of the child node: the condition's children carry their type's
-    ///     instance-declaration NodeIds (<c>i=9189</c> for UnshelveTime), so a direct Read reaches the type, not
-    ///     this condition.
+    ///     clause, which is what an alarm client consumes. (A direct Read of the child also works since Gitea
+    ///     #629 gave condition children instance-scoped NodeIds — see <c>ConditionChildNodeIdTests</c>.)
     /// </remarks>
     [Fact]
     public async Task A_scripted_timed_shelve_reports_the_real_remaining_unshelve_time()