Add prompt cache control loading

internal/promptdef/filesystem_repository.go

@@ -42,9 +42,15 @@ type promptInputFile struct {
 }
 
 type promptMessageFile struct {
-	Role        string `yaml:"role"`
-	Content     string `yaml:"content"`
-	ContentFile string `yaml:"content_file"`
+	Role         string            `yaml:"role"`
+	Content      string            `yaml:"content"`
+	ContentFile  string            `yaml:"content_file"`
+	CacheControl *cacheControlFile `yaml:"cache_control"`
+}
+
+type cacheControlFile struct {
+	Type string `yaml:"type"`
+	TTL  string `yaml:"ttl"`
 }
 
 type promptOutputContractFile struct {
@@ -212,6 +218,11 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 			return nil, fmt.Errorf("message %d (%s) must set exactly one of content or content_file", i, role)
 		}
 
+		cacheControl, err := normalizeCacheControl(msg.CacheControl)
+		if err != nil {
+			return nil, fmt.Errorf("message %d (%s) cache_control: %w", i, role, err)
+		}
+
 		templateContent := msg.Content
 		resolvedContentFile := ""
 		if hasContentFile {
@@ -230,9 +241,10 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 		}
 
 		templates = append(templates, domain.PromptMessageTemplate{
-			Role:        role,
-			Content:     templateContent,
-			ContentFile: resolvedContentFile,
+			Role:         role,
+			Content:      templateContent,
+			ContentFile:  resolvedContentFile,
+			CacheControl: cacheControl,
 		})
 	}
 
@@ -274,6 +286,30 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 	}, nil
 }
 
+func normalizeCacheControl(raw *cacheControlFile) (*domain.CacheControl, error) {
+	if raw == nil {
+		return nil, nil
+	}
+
+	cacheType := strings.TrimSpace(raw.Type)
+	if cacheType == "" {
+		return nil, errors.New("type is required")
+	}
+	if domain.CacheControlType(cacheType) != domain.CacheControlEphemeral {
+		return nil, fmt.Errorf("unsupported type %q", cacheType)
+	}
+
+	ttl := strings.TrimSpace(raw.TTL)
+	if ttl != "" && ttl != "1h" {
+		return nil, fmt.Errorf("unsupported ttl %q", ttl)
+	}
+
+	return &domain.CacheControl{
+		Type: domain.CacheControlType(cacheType),
+		TTL:  ttl,
+	}, nil
+}
+
 func isValidOutputFormat(f domain.OutputFormat) bool {
 	switch f {
 	case domain.FormatText, domain.FormatMarkdown, domain.FormatJSON: