chore(sdk): update thread object (#1843)

Co-authored-by: David Duong <david@duong.cz>

.changeset/nasty-flowers-enjoy.md

@@ -0,0 +1,5 @@
+---
+"@langchain/langgraph-sdk": patch
+---
+
+Expose `Thread["config"]` and `Thread["error"]` 

libs/sdk/src/schema.ts

@@ -211,6 +211,12 @@ export interface Thread<ValuesType = DefaultValues> {
 
   /** Interrupts which were thrown in this thread */
   interrupts: Record<string, Array<Interrupt>>;
+
+  /** The config for the thread */
+  config?: Config;
+
+  /** The error for the thread (if status == "error") */
+  error?: Optional<string | Record<string, unknown>>;
 }
 
 export interface Cron {