feat: add natural-language-cli-agentkit tutorial

[jadonamite]

Summary

Adds a step-by-step guide for setting up a CDP AgentKit Wallet with LangChain to execute natural language commands via a CLI.

Content

• Author: @jadonamite
• Stack: Node.js, LangChain, AgentKit (CDP), OpenAI.
• Key Concepts:
  • CdpWalletProvider configuration and persistence (handling wallet_data.txt).
  • Interactive REPL loop implementation using readline.
  • Integration of cdpWalletActionProvider for asset swaps and transfers.

Motivation

This fulfills the need for a "Hello World" guide that focuses purely on the wallet setup and command interaction flow, separate from autonomous looping agents.

Verification

• Verified wallet_data.txt creation and persistence.
• Tested "Request funds from faucet" command on Base Sepolia.
• Tested "Swap ETH for USDC" command.

[cb-heimdall]

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