agent-ui demo

Setup

Clone langgraph repo and langgraphjs-api repo.
Checkout the following branches:
- langgraph: dqbd/sdk-js-react-ui
- langgraphjs-api: dqbd/api-ui
Run npx packserve -d ../langgraph/libs/sdk-js ../langgraphjs-api/libs/langgraph-api ../langgraphjs-api/libs/langgraph-cli
Run pnpm install while running the packserve server

TODO: will create RC packages down the line, but just too lazy for now.