refactor: 将结构哈希与常量类从编译器拆分

crates/oxide_compiler/src/module.rs

@@ -1,8 +1,16 @@
 use std::fmt;
 
-use crate::compiler::Constant;
 use crate::opcode::{self, OpCode};
 
+#[derive(Debug, Clone, PartialEq)]
+pub enum Constant {
+    Number(f64),
+    String(String),
+    Boolean(bool),
+    Null,
+    Undefined,
+}
+
 pub struct CompiledModule {
     pub bytecode: Vec<opcode::Instr>,
     pub constants: Vec<Constant>,