fix(core): skip cancellation notification for initialize requests

[ameenalkhaldi]

Summary

Fixes #998.

Per the MCP specification, clients must not cancel the initialize request:

A client MUST NOT attempt to cancel its initialize request.
(cancellation.mdx §2, mirrored in packages/core/src/types/types.ts)

Before this change, when Client.connect() received an AbortSignal that later aborted, or when the initialize request timed out, Protocol._requestWithSchema unconditionally sent notifications/cancelled to the server for the in-flight initialize request.

Fix

In cancel() inside _requestWithSchema (packages/core/src/shared/protocol.ts), guard the outbound notifications/cancelled send on request.method !== 'initialize'. The abort/reject path is unchanged — the caller's promise still rejects with the supplied reason — only the wire notification is suppressed for initialize.

Tests

Added three cases in packages/core/test/shared/protocol.test.ts under a new initialize request cancellation describe block:

• aborting an initialize request does not send notifications/cancelled
• timing out an initialize request does not send notifications/cancelled
• aborting a non-initialize request still sends notifications/cancelled (regression guard)

Test plan

• pnpm typecheck:all
• pnpm lint:all
• pnpm test:all (all packages green, 492/492 in core)
• pnpm build:all

[changeset-bot]

🦋 Changeset detected

Latest commit: 52478f7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@modelcontextprotocol/core	Patch

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