support for cancellation in client and server

[Mehdi-Bl]

Describe the bug
How to cancel tools execution.
We have a side issue about having a cancel notification for process over 10s.
The issue when a tool start and we want to stop. Pressing stop button on Claude Desktop is supposed to send signal to stop it.
This seem not implemented in SDK current workflow or notification types.

To Reproduce
Cancel tool that started running before it terminates.

Expected behavior
MCP Server recieve a ntoficiation for cancellation ==> sig term or equivalent to stop / cleanup the process and respond Stopped.

Desktop (please complete the following information):

• OS: Windows
• Browser Chrome