feat: add transaction analytics and performance metrics

From the current SDK :

You execute:
swaps
bridges
LP ops

But:

❌ no historical tracking
❌ no performance insights
❌ no debugging visibility
❌ no risk analytics

This makes AgentKit blind execution infra

API
await agent.metrics.summary()
Output
```
{
  totalVolume: "10000",
  avgSlippage: "1.2%",
  successRate: "98%"
}
```

Use cases
dashboards
trading insights
debugging