Attach prompt export values in module registry

internal/briefing/modules.go

@@ -21,6 +21,8 @@ type ModuleContext struct {
 
 type ModuleBuilder func(ModuleContext, any) (*module.Output, error)
 
+type ModulePromptExporter func(value any) (any, error)
+
 type ModuleDefinition struct {
 	ID                module.ID
 	StanzaName        string
@@ -31,6 +33,7 @@ type ModuleDefinition struct {
 	MissingData       module.MissingDataBehavior
 	AllowDuplicate    bool
 	Builder           ModuleBuilder
+	PromptExporter    ModulePromptExporter
 }
 
 type ModuleRegistry struct {
@@ -130,6 +133,15 @@ func (r ModuleRegistry) BuildModule(ctx ModuleContext, item module.ConfigItem) (
 	if output.StanzaName != definition.StanzaName {
 		return nil, fmt.Errorf("module %q produced stanza %q, want %q", definition.ID, output.StanzaName, definition.StanzaName)
 	}
+	if definition.PromptExporter == nil {
+		output.PromptValue = output.Value
+		return output, nil
+	}
+	promptValue, err := definition.PromptExporter(output.Value)
+	if err != nil {
+		return nil, fmt.Errorf("module %q stanza %q prompt export: %w", definition.ID, definition.StanzaName, err)
+	}
+	output.PromptValue = promptValue
 	return output, nil
 }