fix(docs): resolve TypeScript type errors in LangGraph QuickStart tutorial

[EstoesMoises]

Overview

Fixed TypeScript type errors and deprecated API usage in the LangGraph quickstart tutorial.

Graph API (main changes):

• Migrated state definition from Zod to Annotation API to resolve type incompatibilities
• Replaced deprecated isAIMessage() with AIMessage.isInstance()
• Replaced deprecated .getType() with .type property

Functional API:

• Updated to use AIMessage.isInstance() and .type property for consistency
• Removed unused import from "Step 4: Define agent"

These changes eliminate typecheck errors while keeping the example clear and easy to follow.

Type of change

Type: Update existing documentation

Related issues/PRs

It resolves - langchain-ai/langgraph#6517

Checklist

• I have read the contributing guidelines
• I have tested my changes locally using docs dev
• All code examples have been tested and work correctly
• I have used root relative paths for internal links
• I have updated navigation in src/docs.json if needed

[lnhsingh]

Thank you!

[Copilot]

Pull request overview

This PR fixes TypeScript type errors in the LangGraph quickstart tutorial by migrating from Zod-based state definitions to the Annotation API, replacing deprecated message API methods, and removing unused imports. The changes eliminate typecheck errors while maintaining clarity and consistency across both the Graph API and Functional API examples.

Key changes:

• Migrated state definition from Zod (z.object()) to Annotation API (Annotation.Root()) with proper reducer functions
• Replaced deprecated isAIMessage() with AIMessage.isInstance() for type checking
• Replaced deprecated .getType() method with .type property for accessing message types
• Added language-specific documentation tips explaining state management differences