fix(core): clear recently-cancelled request ids on connection close

[devcrocod]

Clear the recently-cancelled request id buffer in doClose so connection teardown fully resets per-request bookkeeping.

Motivation and Context

Follow-up to #884. doClose already resets _responseHandlers, _progressHandlers, and inFlightRequestJobs, but left recentlyCancelledRequestIds populated across a close. This aligns teardown to clear all Protocol-scoped per-request state.

Not a correctness bug: the buffer is bounded (256) and self-evicting, request ids are random UUIDs so stale entries cannot false-match a new connection, and the post-close onMessage guard drops late messages from the old transport before the buffer is consulted. The change removes the lone asymmetry in doClose.

How Has This Been Tested?

• ./gradlew :kotlin-sdk-core:compileKotlinJvm
• ./gradlew :kotlin-sdk-core:jvmTest --tests "*ProtocolTest*"

Breaking Changes

None.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

recentlyCancelledRequestIds is Protocol-scoped (like _responseHandlers/_progressHandlers), so it is reset in doClose rather than on the per-connection Connection object.

[Copilot]

Pull request overview

This PR updates the core Protocol connection teardown path to fully reset Protocol-scoped per-request bookkeeping by clearing the buffer of recently-cancelled outbound request IDs during doClose. This aligns recentlyCancelledRequestIds cleanup with the existing teardown behavior for response handlers, progress handlers, and in-flight request jobs.

Changes:

• Clear recentlyCancelledRequestIds during Protocol.doClose(...) to avoid carrying buffered cancellations across a close/reconnect.
• Keep teardown symmetry with other Protocol-scoped request tracking structures (_responseHandlers, _progressHandlers, inFlightRequestJobs).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.