Function rv_kind_mem_class 

pub fn rv_kind_mem_class(kind: u8) -> MemClass

Classify a gas kind as a category-#3 memory op. Uses the same exec_unit == EU_LOAD/EU_STORE predicate rv_feed_gas_kind uses for the #2 mem_cycles override (gas_cost.rs), so “memory op for #3” and “memory op for #2” provably agree across both engines.