Require validation preparation internally

internal/usecase/runner.go

@@ -49,7 +49,7 @@ type Runner struct {
 	artifacts               artifact.Reader
 	renderer                prompt.Renderer
 	llm                     llm.Client
-	validator               validate.Validator
+	validator               validate.ValidationPreparer
 	repairer                OutputRepairer
 	admitter                RunAdmitter
 	defaultTransientRetries uint64
@@ -87,7 +87,7 @@ func NewRunner(
 	artifacts artifact.Reader,
 	renderer prompt.Renderer,
 	llmClient llm.Client,
-	validator validate.Validator,
+	validator validate.ValidationPreparer,
 	admitter RunAdmitter,
 ) *Runner {
 	return NewRunnerWithRepairer(
@@ -108,7 +108,7 @@ func NewRunnerWithRepairer(
 	artifacts artifact.Reader,
 	renderer prompt.Renderer,
 	llmClient llm.Client,
-	validator validate.Validator,
+	validator validate.ValidationPreparer,
 	repairer OutputRepairer,
 	admitter RunAdmitter,
 	defaultTransientRetries ...uint64,
@@ -409,11 +409,7 @@ func (r *Runner) prepareValidation(
 	if r.validator == nil {
 		return noOpPreparedValidation{contract: contract}, nil
 	}
-	preparer, ok := r.validator.(validate.ValidationPreparer)
-	if !ok {
-		return nil, fmt.Errorf("%w: validator does not support prepared validation", ErrValidation)
-	}
-	plan, err := preparer.PrepareValidation(ctx, contract)
+	plan, err := r.validator.PrepareValidation(ctx, contract)
 	if err != nil {
 		return nil, &OperationError{Category: ErrValidation, Cause: err}
 	}