E2E test: Connection resilience — operations after socket error

[s2x]

Closes #170

Problem

No E2E test verifies client behavior when the underlying TCP socket encounters an error mid-session. In production, network partitions, server restarts, and load balancer timeouts cause socket errors.

Expected tests

public function testOperationAfterSocketDisconnect(): void
{
    $connection = Connection::create(...);
    $streamName = 'test-resilience-' . uniqid();
    $connection->createStream($streamName);

    // Simulate socket error by stopping Docker container
    // or closing the socket via reflection

    $this->expectException(\RuntimeException::class);
    $connection->createStream('another-stream');
}

public function testIsConnectedReturnsFalseAfterSocketError(): void
{
    // After socket error, isConnected() should return false
}

Why it matters

• Network failures are inevitable in production
• The client must fail fast with clear errors, not hang or corrupt state
• readBytes() returns null on SOCKET_ETIMEDOUT but throws on other errors — both paths need testing

Notes

• This test may require Docker manipulation (stop/start container)
• Alternative: use reflection to close the socket directly
• Consider marking as @group slow or @group destructive

Acceptance criteria

• Socket error → clear RuntimeException on next operation
• isConnected() returns false after socket error
• No resource leaks after socket error