feat(srp): add renderer-driven pipeline backbone

Introduce renderer-driven and renderer-backed managed pipeline base types in the Universal package.

Move shared renderer-data/default-renderer ownership out of UniversalRenderPipelineAsset, migrate probe assets onto the generic seam, and expose renderer recording/request context types for future SRP expansion.

Update scripting API-surface expectations and validate with build, unit tests, scripting tests, and old editor smoke.

managed/GameScripts/RenderPipelineApiProbe.cs

@@ -1115,7 +1115,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedRenderPipelineProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public static int CreatePipelineCallCount;
 
@@ -1135,7 +1135,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedPostProcessRenderPipelineProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public ManagedPostProcessRenderPipelineProbeAsset()
         {
@@ -1148,7 +1148,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedUnknownBackendRenderPipelineProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public ManagedUnknownBackendRenderPipelineProbeAsset()
         {
@@ -1188,7 +1188,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedDefaultRendererSelectionProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public ManagedDefaultRendererSelectionProbeAsset()
         {
@@ -1202,7 +1202,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedInvalidDefaultRendererSelectionProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public ManagedInvalidDefaultRendererSelectionProbeAsset()
         {
@@ -1216,7 +1216,7 @@ namespace Gameplay
     }
 
     public sealed class ManagedRendererReuseProbeAsset
-        : UniversalRenderPipelineAsset
+        : RendererBackedRenderPipelineAsset
     {
         public ManagedRendererReuseProbeAsset()
         {