[demo-mcp-2026-05] Pino with destination=2 — cleaner than console redirection for MCP stdio

Console-redirection (console.log = console.error) works to keep MCP stdio's stdout clean, but it is fragile: it has to run before any import that might log at module-eval time, and it does not catch native code or workers that write directly to fd 1. Need a more robust pattern.