Function estimated_bt_strategy_extra_bytes 

pub fn estimated_bt_strategy_extra_bytes(
    strategy_ordinal: u32,
    window_log: u32,
) -> usize

Extra steady-state workspace the optimal strategies (ordinals 7..=9, btopt..btultra2) retain beyond the hash/chain tables: the boxed matcher plus its scratch arenas, and the HC3 short-match side table for btultra/btultra2 (capped by the window log). 0 for the other ordinals (btlazy2’s tree lives in the lazy backend’s chain table).