add error handling for onprogress disconnects (stop server crashing)

[evalstate]

This is a fix to the _onProgress handler to follow the exception pattern used elsewhere in the SDK. At the moment, exceptions in the handler terminate the Node process with:

Specific scenario is usage in a proxy scenario, where Progress Notifications are relayed from the Server to the Client, and the Client disconnects with a close handler.

Error: Not connected
    at Server.notification (/home/shaun/source/typescript-sdk/src/shared/protocol.ts:1282:19)
    at <anonymous> (/home/shaun/source/typescript-sdk/src/examples/server/disconnectTestServer.ts:43:35)
    at async McpServer.executeToolHandler (/home/shaun/source/typescript-sdk/src/server/mcp.ts:352:20)
    at async <anonymous> (/home/shaun/source/typescript-sdk/src/server/mcp.ts:214:32)
    at async wrappedHandler (/home/shaun/source/typescript-sdk/src/server/index.ts:262:32)

To demonstrate the failure:
tsx src/examples/client/disconnectTestServer.ts
tsx src/examples/client/disconnectTestClient.ts

The Client terminates after 5 notifications, triggering the error condition.

Server output after fix:

Sending notification 4/10
Sending notification 5/10
Client disconnected unexpectedly
Transport closed for session: 3de16462-5919-4760-9fb0-a38cd8496b4a
Sending notification 6/10
[onerror] Not connected
Sending notification 7/10
[onerror] Not connected
Sending notification 8/10
[onerror] Not connected
Sending notification 9/10
[onerror] Not connected
Sending notification 10/10
[onerror] Not connected
[onerror] Failed to send response: Error: No connection established for request ID: 1

Notes on the test programs:

• If you don't have a close handler you don't see the exception
• There is an abort controller flag which is the "correct" way to do this (start with --abort to use it) which also avoids the process termination, but could be missed in a production scenario.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/sdk@1282

commit: 5722754