Add integration tests

[cv]

Summary

Add integration tests to verify communication between CLI, Native Host, and Chrome Extension components.

Background

PR #2 added the testing infrastructure with vitest. The test/integration/ directory exists but is empty.

Scope

Integration tests should cover:

CLI ↔ Native Host

• Unix socket connection establishment
• JSON message serialization/deserialization
• Request/response round-trips
• Timeout and error handling

Native Host ↔ Extension

• Native messaging protocol
• Tool request dispatching
• Response handling and formatting

Full Command Flows

• surf tab.list → returns tab data
• surf go <url> → navigates and returns result
• surf screenshot → captures and saves image
• surf read → returns accessibility tree + text

Notes

• May require mocking Chrome APIs (mocks started in test/mocks/)
• Consider using a test extension instance or stubbing the socket
• Related: Add quality and security checks to CI pipeline #4 (CI), PR Add testing infrastructure #2 (test infrastructure)