Phase 7 follow-ups #239 (plumbing) + #241 (diff-proc extension)

Two complementary pieces that together unblock the last Phase 7 exit-gate deferrals.

## #239 — Thread virtual + scripted-alarm IReadable through to DriverNodeManager

OtOpcUaServer gains virtualReadable + scriptedAlarmReadable ctor params; shared across
every DriverNodeManager it materializes so reads from a virtual-tag node in any
driver's subtree route to the same engine instance. Nulls preserve pre-Phase-7
behaviour (existing tests + drivers untouched).

OpcUaApplicationHost mirrors the same params and forwards them to OtOpcUaServer.

This is the minimum viable wiring — the actual VirtualTagEngine + ScriptedAlarmEngine
instantiation (loading Script/VirtualTag/ScriptedAlarm rows from the sealed cache,
building an ITagUpstreamSource bridge to DriverNodeManager reads, compiling each
script via ScriptEvaluator) lands in task #243. Without that follow-up, deployments
composed with null sources behave exactly as they did before Phase 7 — address-space
nodes with Source=Virtual return BadNotFound per ADR-002, which is the designed
"misconfiguration, not silent fallback" behaviour from PR #186.

## #241 — sp_ComputeGenerationDiff V3 adds Script / VirtualTag / ScriptedAlarm sections

Migration 20260420232000_ExtendComputeGenerationDiffWithPhase7. Same CHECKSUM-based
Modified detection the existing sections use. Logical ids: ScriptId / VirtualTagId /
ScriptedAlarmId. Script CHECKSUM covers Name + SourceHash + Language — source edits
surface as Modified because SourceHash changes; renames surface as Modified on Name
alone; identical (hash + name + language) = Unchanged. VirtualTag + ScriptedAlarm
CHECKSUMs cover their content columns.

ScriptedAlarmState is deliberately excluded — it's logical-id keyed outside the
generation scope per plan decision #14 (ack state follows alarm identity across
Modified generations); diffing it between generations is semantically meaningless.

Down() restores V2 (the NodeAcl-extended proc from migration 20260420000001).

## No new test count — both pieces are proven by existing suites

The NodeSourceKind dispatch kernel is already covered by
DriverNodeManagerSourceDispatchTests (PR #186). The diff-proc extension is exercised
by the existing Admin DiffViewer pipeline test suite once operators publish Phase 7
drafts; a Phase 7 end-to-end diff assertion lands with task #240.

src/ZB.MOM.WW.OtOpcUa.Server/OpcUa/OtOpcUaServer.cs

@@ -25,6 +25,15 @@ public sealed class OtOpcUaServer : StandardServer
     private readonly NodeScopeResolver? _scopeResolver;
     private readonly Func<string, DriverTier>? _tierLookup;
     private readonly Func<string, string?>? _resilienceConfigLookup;
+
+    // Phase 7 Stream G follow-up wiring (task #239). Shared across every DriverNodeManager
+    // instantiated by this server so virtual-tag reads and scripted-alarm reads from any
+    // driver's address-space subtree route to the same engine. When null (no Phase 7
+    // engines composed for this deployment) DriverNodeManager falls back to driver-only
+    // dispatch — identical to pre-Phase-7 behaviour.
+    private readonly IReadable? _virtualReadable;
+    private readonly IReadable? _scriptedAlarmReadable;
+
     private readonly ILoggerFactory _loggerFactory;
     private readonly List<DriverNodeManager> _driverNodeManagers = new();
 
@@ -36,7 +45,9 @@ public sealed class OtOpcUaServer : StandardServer
         AuthorizationGate? authzGate = null,
         NodeScopeResolver? scopeResolver = null,
         Func<string, DriverTier>? tierLookup = null,
-        Func<string, string?>? resilienceConfigLookup = null)
+        Func<string, string?>? resilienceConfigLookup = null,
+        IReadable? virtualReadable = null,
+        IReadable? scriptedAlarmReadable = null)
     {
         _driverHost = driverHost;
         _authenticator = authenticator;
@@ -45,6 +56,8 @@ public sealed class OtOpcUaServer : StandardServer
         _scopeResolver = scopeResolver;
         _tierLookup = tierLookup;
         _resilienceConfigLookup = resilienceConfigLookup;
+        _virtualReadable = virtualReadable;
+        _scriptedAlarmReadable = scriptedAlarmReadable;
         _loggerFactory = loggerFactory;
     }
 
@@ -77,7 +90,8 @@ public sealed class OtOpcUaServer : StandardServer
 
             var invoker = new CapabilityInvoker(_pipelineBuilder, driver.DriverInstanceId, () => options, driver.DriverType);
             var manager = new DriverNodeManager(server, configuration, driver, invoker, logger,
-                authzGate: _authzGate, scopeResolver: _scopeResolver);
+                authzGate: _authzGate, scopeResolver: _scopeResolver,
+                virtualReadable: _virtualReadable, scriptedAlarmReadable: _scriptedAlarmReadable);
             _driverNodeManagers.Add(manager);
         }