Refactor: separate prompt/profile run resolution with explicit precedence, centralized defaults, and api_key_env validation

internal/usecase/runner.go

@@ -8,10 +8,12 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/artifact"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
@@ -102,13 +104,16 @@ func (r *Runner) Run(ctx context.Context, req domain.RunRequest) (*domain.RunRes
 	if err != nil {
 		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, err)
 	}
-	effectiveModel := mergeExecutionTarget(executionProfileToTarget(execProfile), req.Execution)
+	effectiveModel := resolveExecutionTarget(execProfile, req.Execution)
 	if strings.TrimSpace(effectiveModel.Endpoint) == "" {
 		return nil, fmt.Errorf("%w: execution endpoint is required", ErrInvalidRequest)
 	}
 	if strings.TrimSpace(effectiveModel.Model) == "" {
 		return nil, fmt.Errorf("%w: execution model is required", ErrInvalidRequest)
 	}
+	if err := validateAPIKeyEnv(effectiveModel.APIKeyEnv); err != nil {
+		return nil, fmt.Errorf("%w: %w", ErrInvalidRequest, err)
+	}
 	effectiveContract := resolveOutputContract(def, req.Validation)
 
 	resolvedInputs := make(map[string]*domain.Artifact, len(req.Inputs))
@@ -231,11 +236,7 @@ func (r *Runner) shouldAttemptRepair(contract domain.OutputContract, validationR
 	return contract.ValidationMode == domain.ValidationJSON || contract.ValidationMode == domain.ValidationJSONSchema
 }
 
-func mergeExecutionTarget(base domain.ExecutionTarget, override *domain.ExecutionTarget) domain.ExecutionTarget {
-	if override == nil {
-		return base
-	}
-
+func mergeExecutionTarget(base domain.ExecutionTarget, override domain.ExecutionTarget) domain.ExecutionTarget {
 	out := base
 	if override.Endpoint != "" {
 		out.Endpoint = override.Endpoint
@@ -271,6 +272,26 @@ func mergeExecutionTarget(base domain.ExecutionTarget, override *domain.Executio
 	return out
 }
 
+func resolveExecutionTarget(profileValue *domain.ExecutionProfile, override *domain.ExecutionTarget) domain.ExecutionTarget {
+	out := defaults.ExecutionTargetDefault()
+	out = mergeExecutionTarget(out, executionProfileToTarget(profileValue))
+	if override != nil {
+		out = mergeExecutionTarget(out, *override)
+	}
+	return out
+}
+
+func validateAPIKeyEnv(apiKeyEnv string) error {
+	envName := strings.TrimSpace(apiKeyEnv)
+	if envName == "" {
+		return nil
+	}
+	if strings.TrimSpace(os.Getenv(envName)) == "" {
+		return fmt.Errorf("api key environment variable %q is not set", envName)
+	}
+	return nil
+}
+
 func executionProfileToTarget(p *domain.ExecutionProfile) domain.ExecutionTarget {
 	if p == nil {
 		return domain.ExecutionTarget{}
@@ -325,16 +346,16 @@ func buildOutputArtifact(content string, format domain.OutputFormat) domain.Arti
 	body := []byte(content)
 	hash := sha256.Sum256(body)
 
-	contentType := "text/plain"
+	contentType := defaults.ContentTypeTextPlain
 	switch format {
 	case domain.FormatMarkdown:
-		contentType = "text/markdown"
+		contentType = defaults.ContentTypeTextMarkdown
 	case domain.FormatJSON:
-		contentType = "application/json"
+		contentType = defaults.ContentTypeApplicationJSON
 	}
 
 	return domain.Artifact{
-		Name:        "output",
+		Name:        defaults.OutputArtifactName,
 		ContentType: contentType,
 		Body:        body,
 		Size:        int64(len(body)),