incorrect reduction of subtraction css-variable from zero

incorrect reduction of subtraction css-variable from zero: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). While https://github.com/postcss/postcss-calc/issues/88 is fixed by https://github.com/postcss/postcss-calc/pull/93 , this case still has bug: calc(0px - (var(--foo…

The task

While https://github.com/postcss/postcss-calc/issues/88 is fixed by https://github.com/postcss/postcss-calc/pull/93 , this case still has bug: calc(0px - (var(--foo, 4px) / 2)) is reduced into: calc(var(--foo, 4px)/2)

Part of XiaomiMiMo/MiMo-V2.6-RL-oss.