Add Integration Tests with Real Ethereum Nodes

Summary

Our test suite only uses Anvil, which doesn't accurately replicate real execution client behavior. As seen in Robust-Provider#6 there are non-trivial differences between Anvil and real clients (Geth, Nethermind, Reth, etc.) that cause production issues. We need integration tests against variety of real nodes for a stable release.

Problem

• Anvil differs from production clients in WebSocket behavior, error responses, and RPC semantics
• Bugs may slip through that would be caught with real client testing

Solution

Use ethereum-package via Kurtosis to spin up ephemeral Ethereum networks with real execution clients for integration testing.

Tasks

• Add Kurtosis to CI pipeline
• Create integration test suite (feature-gated, separate from unit tests)
• Test against multiple clients: Geth, Nethermind, Reth
• Cover key scenarios: subscriptions, reconnection, error handling
• Run on merges to main and release branches (not every PR)

No repository files or tests are named. Start by locating the CI configuration and the existing Anvil-backed tests, then review how integration tests are separated and feature-gated; done means Kurtosis can launch Geth, Nethermind, and Reth networks and merge/release runs cover subscriptions, reconnection, and error handling.