feat: 字节码VM基础设施 — 编译器、VM执行循环、Runtime trait

Phase 1-3: 基础VM架构
- 新增 Runtime trait: 抽象树遍历解释器和VM的共同接口
- NativeFn 改为接受 &mut dyn Runtime
- 重构所有内置函数使用新签名
- vm/opcode.rs: 33个字节码指令 + 编码/解码辅助函数
- vm/compiler.rs: AST→字节码编译器，支持变量解析、跳转回填、作用域
- vm/vm.rs: 栈式VM执行循环，支持全局变量、原生函数调用
- lib.rs: 新增 run_file_vm() + --vm CLI标志
- 修复: 跳转偏移计算、对象字面量编译

工作特性: 算术、变量、while/for循环、条件、数组、对象、字符串
待完成: 用户定义函数调用、闭包/upvalue捕获、完整require支持

Release模式: 1M算术循环 VM 0.44s vs 树遍历 0.89s (2.0x加速)

aster-core/src/lib.rs

@@ -2,12 +2,15 @@ pub mod lexer;
 pub mod ast;
 pub mod parser;
 pub mod interpreter;
+pub mod vm;
 pub mod error;
 pub mod analysis;
 
 use lexer::Lexer;
 use parser::Parser;
 use interpreter::Interpreter;
+use vm::compiler::Compiler;
+use vm::vm::Vm;
 use error::RuntimeError;
 
 use std::io::Write;
@@ -46,6 +49,41 @@ pub fn run_file(filename: &str, src: String) {
     }
 }
 
+/// Run a file using the bytecode VM (for performance comparison).
+pub fn run_file_vm(filename: &str, src: String) {
+    let (tokens, lex_errors) = Lexer::new(&src).tokenize();
+    if !lex_errors.is_empty() {
+        print_errors(&lex_errors);
+        std::process::exit(65);
+    }
+
+    let mut parser = Parser::new(tokens);
+    let (stmts, parse_errors) = parser.parse();
+    if !parse_errors.is_empty() {
+        print_errors(&parse_errors);
+        std::process::exit(65);
+    }
+
+    let script_dir = std::path::Path::new(filename)
+        .parent()
+        .map(|p| p.to_string_lossy().to_string())
+        .unwrap_or_else(|| ".".to_string());
+
+    let proto = match Compiler::compile(&stmts) {
+        Ok(p) => p,
+        Err(e) => {
+            eprintln!("Compile Error: {}", e);
+            std::process::exit(70);
+        }
+    };
+
+    let mut vm = Vm::with_current_dir(script_dir);
+    if let Err(e) = vm.run(std::rc::Rc::new(proto)) {
+        eprintln!("Error: {}", e);
+        std::process::exit(70);
+    }
+}
+
 pub fn run_repl() {
     println!("Welcome to Aster REPL!");
     println!("Type ':exit' to quit.");