Fix timeout and listener leaks in readResponseById

[Copilot]

readResponseById never cleared its timeout on success and never removed the data handler on timeout, causing listener accumulation and keeping the test process alive up to timeoutMs per call.

Changes

• Store and clear the timer — capture the setTimeout handle and call clearTimeout(timer) in the success path before resolving
• Detach handler on timeout — call proc.stdout!.off("data", handler) inside the timeout callback before rejecting
• Unref the timer — call timer.unref() so a pending timeout doesn't prevent the event loop from exiting naturally

proc.stdout!.on("data", handler);
const timer = setTimeout(() => {
  proc.stdout!.off("data", handler);          // detach on timeout
  reject(new Error(`Timeout waiting for response id=${id}`));
}, timeoutMs);
timer.unref();                                // don't block event loop exit

// in handler, on match:
proc.stdout!.off("data", handler);
clearTimeout(timer);                          // cancel timer on success
resolve(msg);

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[Copilot]

Pull request overview

This PR fixes resource leaks in the readResponseById test helper function that were causing listener accumulation and preventing the test process from exiting naturally. The function was failing to clear its timeout on success and was not removing event handlers on timeout.

Changes:

• Added proper timeout cleanup on success path by capturing and clearing the timer handle
• Added event handler removal in the timeout callback to prevent listener leaks
• Added timer.unref() to prevent pending timeouts from blocking event loop exit

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[Copilot]

The same timeout and listener leak issues fixed here also exist in packages/mcp-server/test/integration/server.test.ts. That file has two similar functions (readResponse on line 14 and readResponseById on line 38) that also need:

1. The timer handle captured and cleared on success
2. The handler removed on timeout
3. The timer unref'd to prevent blocking event loop exit

Consider applying the same fix pattern to those functions as well.