MCP SDK 1.27+ enforces single-connection per Server instance, throwing
"Already connected to a transport" when connect() is called twice.
Updated test helper to close existing connections before reconnecting.
Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>