set loggingConsumer after client initialization

Expected Behavior

We should be able to set a loggingConsumer on McpClient after querying its capabilities.

var capabilities = client.getServerCapabilities();
if (capabilities.logging() != null) {
    client.setLoggingLevel(McpSchema.LoggingLevel.INFO);
    client.setLoggingConsumer(consumer);
}

Current Behavior

Currently, we can set a loggingConsumer with McpClientTransport before client initialization. For example,

McpClient.sync(server.transport())
                .loggingConsumer(consumer)
                .build();

Context

However, many MCP servers' logging capabilities are not enabled. But we cannot query if the server has this capability before client initialization. Such a poor design makes it impossible to register a logging consumer safely.

まず McpClient の初期化と機能問い合わせのフローを読み、次に McpClientTransport の loggingConsumer 設定と比較します。初期化前に setLoggingLevel と setLoggingConsumer がどのように動作するかを確認します。getServerCapabilities() によって logging のサポートが確認された後に consumer を登録でき、既存の初期化前の builder 使用を壊さなければ完了です。