Fix build errors: add DD_SERVERLESS_COMPAT_PATH to ConfigurationKeys, fix ExporterSettings access path

- Add DD_SERVERLESS_COMPAT_PATH to supported-configurations.yaml so
  the source generator creates ConfigurationKeys.ServerlessCompatPath
- Fix integration classes to use the correct property path:
  Tracer.Instance.Settings.Manager.InitialExporterSettings
- Restore using Datadog.Trace.Configuration (needed for IntegrationId)
- Remove unused System.Reflection/InteropServices from ExporterSettings

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Lewis-E

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/Serverless/CompatibilityLayer_CalculateDogStatsDPipeName_Integration.cs

@@ -9,6 +9,7 @@
 using System;
 using System.ComponentModel;
 using Datadog.Trace.ClrProfiler.CallTarget;
+using Datadog.Trace.Configuration;
 using Datadog.Trace.Logging;
 
 namespace Datadog.Trace.ClrProfiler.AutoInstrumentation.Serverless
@@ -63,7 +64,7 @@ internal static CallTargetReturn<string> OnMethodEnd<TTarget>(
                 // Use the tracer's configured pipe name, which in Azure Functions will be the
                 // unique name generated by ExporterSettings. Fall back to the compat layer's
                 // own calculated name if the tracer isn't initialized yet.
-                var pipeName = Tracer.Instance.Settings?.Exporter?.MetricsPipeName ?? returnValue;
+                var pipeName = Tracer.Instance.Settings?.Manager?.InitialExporterSettings?.MetricsPipeName ?? returnValue;
 
                 Log.Debug(
                     "ServerlessCompat integration: Overriding compat layer DogStatsD pipe name. " +

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/Serverless/CompatibilityLayer_CalculateTracePipeName_Integration.cs

@@ -9,6 +9,7 @@
 using System;
 using System.ComponentModel;
 using Datadog.Trace.ClrProfiler.CallTarget;
+using Datadog.Trace.Configuration;
 using Datadog.Trace.Logging;
 
 namespace Datadog.Trace.ClrProfiler.AutoInstrumentation.Serverless
@@ -63,7 +64,7 @@ internal static CallTargetReturn<string> OnMethodEnd<TTarget>(
                 // Use the tracer's configured pipe name, which in Azure Functions will be the
                 // unique name generated by ExporterSettings. Fall back to the compat layer's
                 // own calculated name if the tracer isn't initialized yet.
-                var pipeName = Tracer.Instance.Settings?.Exporter?.TracesPipeName ?? returnValue;
+                var pipeName = Tracer.Instance.Settings?.Manager?.InitialExporterSettings?.TracesPipeName ?? returnValue;
 
                 Log.Debug(
                     "ServerlessCompat integration: Overriding compat layer trace pipe name. " +

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/Serverless/ServerlessCompatPipeNameHelper.cs

@@ -77,7 +77,7 @@ internal static bool IsCompatLayerAvailableWithPipeSupport(
                 // DD_SERVERLESS_COMPAT_PATH overrides the default binary location
                 // (matches CompatibilityLayer.cs in datadog-serverless-compat-dotnet).
                 const string defaultCompatBinaryPath = @"C:\home\site\wwwroot\datadog\bin\windows-amd64\datadog-serverless-compat.exe";
-                var compatBinaryPath = Util.EnvironmentHelpers.GetEnvironmentVariable("DD_SERVERLESS_COMPAT_PATH")
+                var compatBinaryPath = Util.EnvironmentHelpers.GetEnvironmentVariable(Configuration.ConfigurationKeys.ServerlessCompatPath)
                     ?? defaultCompatBinaryPath;
 
                 // Check that the compat DLL exists and has a version that supports named pipes.

tracer/src/Datadog.Trace/Configuration/supported-configurations.yaml

@@ -1468,6 +1468,14 @@ supportedConfigurations:
       Match all spans that start with "cart" without any limits and any operation name.
           "[{"service": "cart*"}]"
       <seealso cref="Datadog.Trace.Configuration.TracerSettings.SpanSamplingRules"/>
+  DD_SERVERLESS_COMPAT_PATH:
+  - implementation: A
+    type: string
+    default: null
+    const_name: ServerlessCompatPath
+    documentation: |-
+      Overrides the default path to the serverless compat layer binary.
+      Default value is <c>C:\home\site\wwwroot\datadog\bin\windows-amd64\datadog-serverless-compat.exe</c>.
   DD_SYMBOL_DATABASE_BATCH_SIZE_BYTES:
   - implementation: A
     type: int