feat(mcp): support the 2026-07-28 protocol revision and its subscription stream #129

cyclops connects to MCP servers with the initialize handshake. The 2026-07-28 protocol revision is stateless (server/discover) and delivers tool list changes only on a subscriptions/listen stream, so a server that announces changes only that way never reaches cyclops, and its tool list goes stale.

Proposal Support the 2026-07-28 revision once mcp 2.x support lands (#124): negotiate the revision, and for servers that use it, keep one listen stream per server for tool list changes, with the same reconnect and cleanup guarantees as the session today. Check how mcp's own Client (mode="auto") and other clients handle it before choosing between using Client and extending the current connection.