Function fuzz_msg_value 

pub fn fuzz_msg_value() -> impl Strategy<Value = Option<Uint<256, 4>>>

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

Most calls (85%) carry no value. The remaining 15% delegate 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.