ADR-001 last-mile — Program.cs composes EquipmentNodeWalker into the production boot path. Closes task #214 + fully lands ADR-001 Option A as a live code path, not just a connected set of unit-tested primitives. After this PR a server booted against a real Config DB with Published Equipment rows materializes the UNS tree into the OPC UA address space on startup — the whole walker → wire-in → loader chain (PRs #153, #154, #155, #156) finally fires end-to-end in the production process. DriverEquipmentContentRegistry is the handoff between OpcUaServerService's bootstrap-time populate pass + OpcUaApplicationHost's StartAsync walker invocation. It's a singleton mutable holder with Get/Set/Count + Lock-guarded internal dictionary keyed OrdinalIgnoreCase to match the DriverInstanceId convention used by Equipment / Tag rows + walker grouping. Set-once-per-bootstrap semantics in practice though nothing enforces that at the type level — OpcUaServerService.PopulateEquipmentContentAsync is the only expected writer. Shared-mutable rather than immutable-passed-by-value because the DI graph builds OpcUaApplicationHost before NodeBootstrap has resolved the generation, so the registry must exist at compose time + fill at boot time. Program.cs now registers OpcUaApplicationHost via a factory lambda that threads registry.Get as the equipmentContentLookup delegate PR #155 added to the ctor seam — the one-line composition the earlier PR promised. EquipmentNamespaceContentLoader (from PR #156) is AddScoped since it takes the scoped OtOpcUaConfigDbContext; the populate pass in OpcUaServerService opens one IServiceScopeFactory scope + reuses the same loader + DbContext across every driver query rather than scoping-per-driver. OpcUaServerService.ExecuteAsync gets a new PopulateEquipmentContentAsync step between bootstrap + StartAsync: iterates DriverHost.RegisteredDriverIds, calls loader.LoadAsync per driver at the bootstrapped generationId, stashes non-null results in the registry. Null results are skipped — the wire-in's null-check treats absent registry entries as "this driver isn't Equipment-kind; let DiscoverAsync own the address space" which is the correct backward-compat path for Modbus / AB CIP / TwinCAT / FOCAS. Guarded on result.GenerationId being non-null — a fleet with no Published generation yet boots cleanly into a UNS-less address space and fills the registry on the next restart after first publish. Ctor on OpcUaServerService gained two new dependencies (DriverEquipmentContentRegistry + IServiceScopeFactory). No test file constructs OpcUaServerService directly so no downstream test breakage — the BackgroundService is only wired via DI in Program.cs. Four new DriverEquipmentContentRegistryTests: Get-null-for-unknown, Set-then-Get, case-insensitive driver-id lookup, Set-overwrites-existing. Server.Tests 190/190 (was 186, +4 new registry tests). Full ADR-001 Option A now lives at every layer: Core.OpcUa walker (#153) → ScopePathIndexBuilder (#154) → OpcUaApplicationHost wire-in (#155) → EquipmentNamespaceContentLoader (#156) → this PR's registry + Program.cs composition. The last pending loose end (full-integration smoke test that boots Program.cs against a seeded Config DB + verifies UNS tree via live OPC UA client) isn't strictly necessary because PR #155's OpcUaEquipmentWalkerIntegrationTests already proves the wire-in at the OPC UA client-browse level — the Program.cs composition added here is purely mechanical + well-covered by the four-file audit trail plus registry unit tests.

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

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

@@ -86,7 +86,25 @@ builder.Services.AddSingleton<IUserAuthenticator>(sp => ldapOptions.Enabled
 builder.Services.AddSingleton<ILocalConfigCache>(_ => new LiteDbConfigCache(options.LocalCachePath));
 builder.Services.AddSingleton<DriverHost>();
 builder.Services.AddSingleton<NodeBootstrap>();
-builder.Services.AddSingleton<OpcUaApplicationHost>();
+
+// ADR-001 Option A wiring — the registry is the handoff between OpcUaServerService's
+// bootstrap-time population pass + OpcUaApplicationHost's StartAsync walker invocation.
+// DriverEquipmentContentRegistry.Get is the equipmentContentLookup delegate that PR #155
+// added to OpcUaApplicationHost's ctor seam.
+builder.Services.AddSingleton<DriverEquipmentContentRegistry>();
+builder.Services.AddScoped<EquipmentNamespaceContentLoader>();
+
+builder.Services.AddSingleton<OpcUaApplicationHost>(sp =>
+{
+    var registry = sp.GetRequiredService<DriverEquipmentContentRegistry>();
+    return new OpcUaApplicationHost(
+        sp.GetRequiredService<OpcUaServerOptions>(),
+        sp.GetRequiredService<DriverHost>(),
+        sp.GetRequiredService<IUserAuthenticator>(),
+        sp.GetRequiredService<ILoggerFactory>(),
+        sp.GetRequiredService<ILogger<OpcUaApplicationHost>>(),
+        equipmentContentLookup: registry.Get);
+});
 builder.Services.AddHostedService<OpcUaServerService>();
 
 // Central-config DB access for the host-status publisher (LMX follow-up #7). Scoped context