E2E test: Consumer::close() with autoCommit stores final offset

[s2x]

Closes #168

Problem

Consumer::close() has logic to auto-commit the last offset when autoCommit > 0 and name !== null:

if ($this->autoCommit > 0 && $this->name !== null && $this->messagesProcessed > 0) {
    $this->storeOffset($this->lastOffset);
}

No E2E test verifies this behavior. The consumer_auto_commit.php example uses it, but there's no automated test.

Expected test

public function testAutoCommitOnClose(): void
{
    $consumerName = 'auto-commit-test-' . uniqid();

    // Publish 5 messages
    $producer->sendBatch([...]);
    $producer->waitForConfirms();

    // Create consumer with autoCommit
    $consumer = $connection->createConsumer(
        $stream, OffsetSpec::first(),
        name: $consumerName,
        autoCommit: 3
    );

    // Read all messages
    $messages = [];
    while (count($messages) < 5) {
        $messages = array_merge($messages, $consumer->read(timeout: 1));
    }

    // Close should store the last offset
    $consumer->close();

    // Query offset — should be the last message's offset
    $storedOffset = $connection->queryOffset($consumerName, $stream);
    $this->assertSame($messages[4]->getOffset(), $storedOffset);
}

Why it matters

• Auto-commit on close prevents message loss on graceful shutdown
• The messagesProcessed counter and lastOffset tracking must be correct
• Without this test, a regression could cause offset loss on consumer restart

Acceptance criteria

• Consumer with autoCommit stores offset on close()
• Stored offset matches the last consumed message's offset
• Consumer without autoCommit does NOT store offset on close()
• Consumer with no messages processed does NOT store offset on close()