LangChain Agent - NEAR Yield Farmer

Description

Build a LangChain agent template for yield farmer on NEAR.

**THE VIRAL LOOP:**
User wants yield farmer agent → Uses template → Agent operates on NEAR

**Deliverables:**
1. Complete LangChain agent with tools
2. Configuration options
3. Example usage
4. Published to PyPI and GitHub

**Success Metric:** 20+ uses