Phase 7 follow-up #246 — Phase7Composer + Program.cs wire-in

Activates the Phase 7 engines in production. Loads Script + VirtualTag +
ScriptedAlarm rows from the bootstrapped generation, wires the engines through
the Phase7EngineComposer kernel (#243), starts the DriverSubscriptionBridge feed
(#244), and late-binds the resulting IReadable sources to OpcUaApplicationHost
before OPC UA server start.

## Phase7Composer (Server.Phase7)

Singleton orchestrator. PrepareAsync loads the three Phase 7 row sets in one
DB scope, builds CachedTagUpstreamSource, calls Phase7EngineComposer.Compose,
constructs DriverSubscriptionBridge with one DriverFeed per registered
ISubscribable driver (path-to-fullRef map built from EquipmentNamespaceContent
via MapPathsToFullRefs), starts the bridge.

DisposeAsync tears down in the right order: bridge first (no more events fired
into the cache), then engines (cascades + timers stop), then any disposable sink.

MapPathsToFullRefs: deterministic path convention is
  /{areaName}/{lineName}/{equipmentName}/{tagName}
matching exactly what EquipmentNodeWalker emits into the OPC UA browse tree, so
script literals against the operator-visible UNS tree work without translation.
Tags missing EquipmentId or pointing at unknown Equipment are skipped silently
(Galaxy SystemPlatform-style tags + dangling references handled).

## OpcUaApplicationHost.SetPhase7Sources

New late-bind setter. Throws InvalidOperationException if called after
StartAsync because OtOpcUaServer + DriverNodeManagers capture the field values
at construction; mutation post-start would silently fail.

## OpcUaServerService

After bootstrap loads the current generation, calls phase7Composer.PrepareAsync
+ applicationHost.SetPhase7Sources before applicationHost.StartAsync. StopAsync
disposes Phase7Composer first so the bridge stops feeding the cache before the
OPC UA server tears down its node managers (avoids in-flight cascades surfacing
as noisy shutdown warnings).

## Program.cs

Registers IAlarmHistorianSink as NullAlarmHistorianSink.Instance (task #247
swaps in the real Galaxy.Host-writer-backed SqliteStoreAndForwardSink), Serilog
root logger, and Phase7Composer singleton.

## Tests — 5 new Phase7ComposerMappingTests = 34 Phase 7 tests total

Maps tag → walker UNS path, skips null EquipmentId, skips unknown Equipment
reference, multiple tags under same equipment map distinctly, empty content
yields empty map. Pure functions; no DI/DB needed.

The real PrepareAsync DB query path can't be exercised without SQL Server in
the test environment — it's exercised by the live E2E smoke (task #240) which
unblocks once #247 lands.

## Phase 7 production wiring chain status
- ✅ #243 composition kernel
- ✅ #245 scripted-alarm IReadable adapter
- ✅ #244 driver bridge
- ✅ #246 this — Program.cs wire-in
- 🟡 #247 — Galaxy.Host SqliteStoreAndForwardSink writer adapter (replaces NullSink)
- 🟡 #240 — live E2E smoke (unblocks once #247 lands)

src/ZB.MOM.WW.OtOpcUa.Server/OpcUaServerService.cs

@@ -3,6 +3,7 @@ using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using ZB.MOM.WW.OtOpcUa.Core.Hosting;
 using ZB.MOM.WW.OtOpcUa.Server.OpcUa;
+using ZB.MOM.WW.OtOpcUa.Server.Phase7;
 
 namespace ZB.MOM.WW.OtOpcUa.Server;
 
@@ -17,6 +18,7 @@ public sealed class OpcUaServerService(
     DriverHost driverHost,
     OpcUaApplicationHost applicationHost,
     DriverEquipmentContentRegistry equipmentContentRegistry,
+    Phase7Composer phase7Composer,
     IServiceScopeFactory scopeFactory,
     ILogger<OpcUaServerService> logger) : BackgroundService
 {
@@ -34,12 +36,19 @@ public sealed class OpcUaServerService(
         // Skipped when no generation is Published yet — the fleet boots into a UNS-less
         // address space until the first publish, then the registry fills on next restart.
         if (result.GenerationId is { } gen)
+        {
             await PopulateEquipmentContentAsync(gen, stoppingToken);
 
-        // PR 17: stand up the OPC UA server + drive discovery per registered driver. Driver
-        // registration itself (RegisterAsync on DriverHost) happens during an earlier DI
-        // extension once the central config DB query + per-driver factory land; for now the
-        // server comes up with whatever drivers are in DriverHost at start time.
+            // Phase 7 follow-up #246 — load Script + VirtualTag + ScriptedAlarm rows,
+            // compose VirtualTagEngine + ScriptedAlarmEngine, start the driver-bridge
+            // feed. SetPhase7Sources MUST run before applicationHost.StartAsync because
+            // OtOpcUaServer + DriverNodeManager construction captures the field values
+            // — late binding after server start is rejected with InvalidOperationException.
+            // No-op when the generation has no virtual tags or scripted alarms.
+            var phase7 = await phase7Composer.PrepareAsync(gen, stoppingToken);
+            applicationHost.SetPhase7Sources(phase7.VirtualReadable, phase7.ScriptedAlarmReadable);
+        }
+
         await applicationHost.StartAsync(stoppingToken);
 
         logger.LogInformation("OtOpcUa.Server running. Hosted drivers: {Count}", driverHost.RegisteredDriverIds.Count);
@@ -57,6 +66,11 @@ public sealed class OpcUaServerService(
     public override async Task StopAsync(CancellationToken cancellationToken)
     {
         await base.StopAsync(cancellationToken);
+        // Dispose Phase 7 first so the bridge stops feeding the cache + the engines
+        // stop firing alarm/historian events before the OPC UA server tears down its
+        // node managers. Otherwise an in-flight cascade could try to push through a
+        // disposed source and surface as a noisy shutdown warning.
+        await phase7Composer.DisposeAsync();
         await applicationHost.DisposeAsync();
         await driverHost.DisposeAsync();
     }