Function fuzz_msg_value 

pub fn fuzz_msg_value(
    payable_value_weight: u32,
) -> BoxedStrategy<Option<Uint<256, 4>>>

Returns a proptest strategy for generating random msg.value for payable functions.

Most calls carry no value. The configured non-zero percent delegates to UintStrategy, which biases toward edge cases (around 0 / max) and dictionary fixtures, with random fallback. Over-budget values are clamped to sender balance at execute time.