feat: Implement MockWebSocket and MockWebSocketConnector for testing

- Added MockWebSocket class to simulate WebSocket behavior for unit tests.
- Created MockWebSocketConnector extending WebSocketConnectorBase to facilitate controlled WebSocket connections in tests.
- Enhanced NodeWebSocketConnector to improve connection management and error handling.
- Updated WebSocketConnectorBase to include a subscribe method for message handling.
- Introduced idle timeout configuration in WebSocketOptions for better connection management.
- Added comprehensive tests for MockWebSocket and MockWebSocketConnector to cover various scenarios including connection, message handling, and error simulation.
- Created edge case tests for WebSocketConnectorBase to ensure robustness against connection failures and idle disconnections.
- Updated vitest configuration to exclude non-executable files from coverage reports.

Author: electricessence