chore(interpreter): fix small bugs

src/operands.rs

@@ -151,7 +151,7 @@ impl From<usize> for ImmediateOperand {
 impl Into<Word> for ImmediateOperand {
     fn into(self) -> u16 {
         match self {
-            ImmediateOperand::Byte(_) => self.sign_extend().into(),
+            ImmediateOperand::Byte(b) => b as Word,
             ImmediateOperand::Word(w) => w,
         }
     }