io.modelcontextprotocol.client.transport.StdioClientTransport#closeGracefully

从 io.modelcontextprotocol.client.transport.StdioClientTransport#closeGracefully 开始，并复现 issue 中的 Windows npx.cmd 示例。调查启动的进程及其子进程是如何被终止的；完成的标准是关闭 client 后，子进程树也会结束，并且 main 方法可以正常返回。

Bug description
When npx is launched on Windows, a related subprocess is initiated. When using the io.modelcontextprotocol.client.transport.StdioClientTransport#closeGracefully method to close, this.process.destroy() will only terminate the current process, but the subprocess cannot be closed, resulting in the main method not being able to end normally. Therefore, the taskkill pid /F /T command needs to be used to terminate it.

Environment
jdk 17
mcp 0.12.0-SNAPSHOT
windows 11
Steps to reproduce
StdioClientTransport stdioClientTransport = new StdioClientTransport(ServerParameters.builder("D:\dev\nodejs\npx.cmd").args(Arrays.asList("-y","@wopal/mcp-server-hotnews")).build());
McpSyncClient mcpClient = McpClient.sync(stdioClientTransport)
.requestTimeout(Duration.ofSeconds(20L))
.capabilities(McpSchema.ClientCapabilities.builder()
.roots(true)
.sampling()
.build())
.build();
mcpClient.initialize();
McpSchema.ListToolsResult listToolsResult = mcpClient.listTools();
List<McpSchema.Tool> tools = listToolsResult.tools();
System.out.println(tools.get(0).name());
mcpClient.closeGracefully();

Expected behavior
Close the child processes simultaneously

Minimal Complete Reproducible example
StdioClientTransport stdioClientTransport = new StdioClientTransport(ServerParameters.builder("D:\dev\nodejs\npx.cmd").args(Arrays.asList("-y","@wopal/mcp-server-hotnews")).build());
McpSyncClient mcpClient = McpClient.sync(stdioClientTransport)
.requestTimeout(Duration.ofSeconds(20L))
.capabilities(McpSchema.ClientCapabilities.builder()
.roots(true)
.sampling()
.build())
.build();
mcpClient.initialize();
McpSchema.ListToolsResult listToolsResult = mcpClient.listTools();
List<McpSchema.Tool> tools = listToolsResult.tools();
System.out.println(tools.get(0).name());
mcpClient.closeGracefully();