Function sim_or_fund_currency_override 

pub fn sim_or_fund_currency_override(
    trd_env: i32,
    market: Option<i32>,
) -> Option<i32>

Sim-futures and fund accounts expose fixed native currencies.

FUTURES_SIMULATE_JP=13 and legacy backend HK_FUND=13 intentionally alias. trd_env disambiguates the sim-futures branch from real fund backend raw market ids.