chore: record user actions in the session log (#798)

src/response.ts

@@ -41,10 +41,14 @@ export class Response {
   }
 
   addError(error: string) {
-    this._result.push(`Error: ${error}`);
+    this._result.push(error);
     this._isError = true;
   }
 
+  isError() {
+    return this._isError;
+  }
+
   result() {
     return this._result.join('\n');
   }