refactor: 拆分闭包分析与预扫描模块，拆分函数体编译子步骤

crates/oxide_compiler/src/lib.rs

@@ -1,12 +1,14 @@
 #![doc = "OxideJS - AST to bytecode compiler"]
 
 pub mod class;
+pub mod closure;
 pub mod compiler;
 pub mod compiler_log;
 pub mod emit_ctx;
 pub mod expr;
 pub mod hash;
 pub mod ir;
+pub mod prepass;
 pub mod shared;
 pub mod stmt;
 pub mod symbol_table;