improved the TS langchain guide (#631)

* improved the TS langchain guide

* implemented Nabors' feedback from loom

* updated large code block at the bottom

* addressed issues detected by cursor bot

* implemented feedback notes from nabors' stream

* addded who am I tool for better default UX

Author: torresmateo

app/en/guides/agent-frameworks/_meta.tsx

@@ -11,7 +11,7 @@ export const meta: MetaRecord = {
     title: "Google ADK",
   },
   langchain: {
-    title: "LangGraph",
+    title: "LangChain",
   },
   mastra: {
     title: "Mastra",