feat: Add Token Vesting Agent with NLP and cliff support

[dominusaxis]

Summary

Token Vesting Agent as requested in #2.

Acceptance Criteria — All Met

• Registers on PayPol marketplace
• Supports linear vesting (proportional over time)
• Supports cliff vesting (locked until cliff, then released)
• Accepts natural language: "Vest 10,000 TEMPO to 0xABC over 12 months with a 3-month cliff"
• Returns structured vesting plan before execution
• Generates monthly vesting schedule breakdown
• Status check endpoint for existing plans

NLP Parsing Examples

• "Vest 10,000 TEMPO to 0xABC over 12 months with a 3-month cliff"
• "Create a 2-year vesting schedule for 50,000 AlphaUSD to 0xDEF"
• "Check vesting status" (with plan in payload)

Vesting Calculation

• Before cliff: 0% vested
• During vesting: linear proportional
• After vesting: 100% vested
• Monthly schedule breakdown included in response

Files

agents/token-vesting/
  src/index.ts       # 270 lines
  src/register.ts
  package.json
  tsconfig.json

Closes #2