Phase 6.1 Stream A — switch pipeline keys from Guid to string to match IDriver.DriverInstanceId

IDriver.DriverInstanceId is declared as string in Core.Abstractions; keeping
the pipeline key as Guid meant every call site would need .ToString() / Guid.Parse
at the boundary. Switching the Resilience types to string removes that friction
and lets OtOpcUaServer pass driver.DriverInstanceId directly to the builder in
the upcoming server-dispatch wiring PR.

- DriverResiliencePipelineBuilder.GetOrCreate + Invalidate + PipelineKey
- CapabilityInvoker.ctor + _driverInstanceId field

Tests: all 48 Core.Tests still pass. The Invalidate test's keepId / dropId now
use distinct "drv-keep" / "drv-drop" literals (previously both were distinct
Guid.NewGuid() values, which the sed-driven refactor had collapsed to the same
literal — caught pre-commit).

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

src/ZB.MOM.WW.OtOpcUa.Core/Resilience/CapabilityInvoker.cs

@@ -18,7 +18,7 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Resilience;
 public sealed class CapabilityInvoker
 {
     private readonly DriverResiliencePipelineBuilder _builder;
-    private readonly Guid _driverInstanceId;
+    private readonly string _driverInstanceId;
     private readonly Func<DriverResilienceOptions> _optionsAccessor;
 
     /// <summary>
@@ -32,7 +32,7 @@ public sealed class CapabilityInvoker
     /// </param>
     public CapabilityInvoker(
         DriverResiliencePipelineBuilder builder,
-        Guid driverInstanceId,
+        string driverInstanceId,
         Func<DriverResilienceOptions> optionsAccessor)
     {
         ArgumentNullException.ThrowIfNull(builder);

src/ZB.MOM.WW.OtOpcUa.Core/Resilience/DriverResiliencePipelineBuilder.cs

@@ -45,7 +45,7 @@ public sealed class DriverResiliencePipelineBuilder
     /// <param name="capability">Which capability surface is being called.</param>
     /// <param name="options">Per-driver-instance options (tier + per-capability overrides).</param>
     public ResiliencePipeline GetOrCreate(
-        Guid driverInstanceId,
+        string driverInstanceId,
         string hostName,
         DriverCapability capability,
         DriverResilienceOptions options)
@@ -59,7 +59,7 @@ public sealed class DriverResiliencePipelineBuilder
     }
 
     /// <summary>Drop cached pipelines for one driver instance (e.g. on ResilienceConfig change). Test + Admin-reload use.</summary>
-    public int Invalidate(Guid driverInstanceId)
+    public int Invalidate(string driverInstanceId)
     {
         var removed = 0;
         foreach (var key in _pipelines.Keys)
@@ -114,5 +114,5 @@ public sealed class DriverResiliencePipelineBuilder
         return builder.Build();
     }
 
-    private readonly record struct PipelineKey(Guid DriverInstanceId, string HostName, DriverCapability Capability);
+    private readonly record struct PipelineKey(string DriverInstanceId, string HostName, DriverCapability Capability);
 }