Add execution metadata to module specifications

internal/modules/dnd/chunk/scenes/chunker.go

@@ -120,6 +120,7 @@ func ModuleSpec() pipeline.ModuleSpec {
 	return pipeline.ModuleSpec{
 		Key:            Key,
 		Stage:          pipeline.StageChunk,
+		ExecutionClass: contracts.ExecutionClassLLMBacked,
 		Requires:       append([]string(nil), requiredCapabilities...),
 		Provides:       append([]string(nil), providedCapabilities...),
 		ReferenceSlots: shared.ReferenceSlots(referenceSlotDescriptions),

internal/modules/dnd/chunk/scenes/chunker_test.go

@@ -24,6 +24,7 @@ func TestNewModuleSpecAndRegister(t *testing.T) {
 	want := pipeline.ModuleSpec{
 		Key:            Key,
 		Stage:          pipeline.StageChunk,
+		ExecutionClass: contracts.ExecutionClassLLMBacked,
 		Requires:       []string{"source.transcript"},
 		Provides:       []string{"chunks"},
 		ReferenceSlots: wantReferenceSlots(),