Update artifact resolution so configured artifact IDs are resolved through the runtime catalog

internal/artifacts/artifact_resolver.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
@@ -22,6 +23,7 @@ const (
 
 // ErrSessionArtifactNotFound is returned when no readable artifact exists for a known ID.
 var ErrSessionArtifactNotFound = errors.New("session artifact not found")
+var configuredArtifactSourceRE = regexp.MustCompile(`^narratio\.artifact\.[a-z][a-z0-9_]*$`)
 
 type artifactContentKind string
 
@@ -119,6 +121,11 @@ func NormalizeSessionArtifactSource(source string) (string, error) {
 	return normalized, nil
 }
 
+// IsConfiguredArtifactSource returns true when source is narratio.artifact.<name>.
+func IsConfiguredArtifactSource(source string) bool {
+	return configuredArtifactSourceRE.MatchString(strings.TrimSpace(source))
+}
+
 // ResolveSessionArtifact resolves a symbolic source to a readable local session artifact path.
 // Resolution order is manifest producer outputs first, then canonical session path fallback.
 func ResolveSessionArtifact(paths SessionPaths, m *manifest.Manifest, source string) (ResolvedSessionArtifact, error) {
@@ -167,6 +174,35 @@ func ResolveSessionArtifact(paths SessionPaths, m *manifest.Manifest, source str
 	return ResolvedSessionArtifact{}, &SessionArtifactNotFoundError{ArtifactID: spec.ID}
 }
 
+// ResolveSessionArtifactWithCatalog resolves built-in sources using existing rules and resolves
+// configured narratio.artifact.<name> sources through runtime catalog availability.
+func ResolveSessionArtifactWithCatalog(paths SessionPaths, m *manifest.Manifest, source string, catalog *ArtifactCatalog) (ResolvedSessionArtifact, error) {
+	normalized := strings.TrimSpace(source)
+	if !IsConfiguredArtifactSource(normalized) {
+		return ResolveSessionArtifact(paths, m, normalized)
+	}
+	if catalog == nil {
+		return ResolvedSessionArtifact{}, fmt.Errorf("configured artifact source %q requires runtime artifact catalog", source)
+	}
+	entry, ok := catalog.Lookup(normalized)
+	if !ok {
+		return ResolvedSessionArtifact{}, fmt.Errorf("unsupported artifact source %q", source)
+	}
+	if !entry.Available {
+		return ResolvedSessionArtifact{}, &SessionArtifactNotFoundError{ArtifactID: normalized}
+	}
+	if err := validateResolvedContent(entry.Path, contentText); err != nil {
+		return ResolvedSessionArtifact{}, fmt.Errorf("validate %q: %w", normalized, err)
+	}
+	return ResolvedSessionArtifact{
+		ID:            normalized,
+		Path:          filepath.Clean(entry.Path),
+		ProducerStage: entry.ProducerStage,
+		OutputKind:    entry.OutputKind,
+		Provenance:    entry.Provenance,
+	}, nil
+}
+
 func manifestArtifactCandidates(paths SessionPaths, m *manifest.Manifest, spec artifactSpec) []ResolvedSessionArtifact {
 	if m == nil || len(m.Stages) == 0 || spec.ProducerStage == "" || spec.OutputKind == "" {
 		return nil