Add shared metadata maps and stage-name helpers

internal/prompts/registry.go

@@ -40,6 +40,16 @@ type Metadata struct {
 	SHA256        string `json:"sha256"`
 }
 
+func (m Metadata) DiagnosticsMap() map[string]any {
+	return map[string]any{
+		"prompt_id":      m.PromptID,
+		"prompt_version": m.PromptVersion,
+		"prompt_source":  m.PromptSource,
+		"embedded_path":  m.EmbeddedPath,
+		"sha256":         m.SHA256,
+	}
+}
+
 type definition struct {
 	id          string
 	version     string