Probability surface retired

The options and prediction-markets probability surface is withdrawn. /v1/surface/{metal}, /v1/signals/arbitrage, the get_surface MCP tool, and the surface:{metal} WebSocket channel no longer serve; the MCP server is now eight tools. Pro keeps its price and everything else it carried: all three metals, thirty years of daily history, intraday bars, the live oracle stream, and commercial use. Realtime Pro keeps WebSocket ticks and physical channels. No other endpoint, tier, or limit changes, and no key needs replacing.