feat: IDE支持 — workspace拆分、LSP服务器、VS Code扩展

**Workspace 拆分**
- aster-core: 纯库，zero-dependency，包含 lexer/parser/ast/interpreter/error/analysis
- aster: REPL 二进制，薄封装 aster-core
- aster-lsp: LSP 语言服务器

**VS Code 扩展 (vscode-ext/)**
- TextMate 语法高亮 (.ast 文件)
- 语言配置 (注释切换、括号配对、自动缩进)
- LSP 客户端 (extension.js)

**LSP 服务端功能**
- Diagnostics: 实时显示 lex/parse 错误红色波浪线
- Completion: 关键字 + 内置函数 + 用户定义符号补全
- Hover: 悬停显示变量/函数信息
- Signature Help: 函数参数提示
- Goto Definition: Ctrl+Click 跳转到声明处
- Find References: 查找所有引用位置
- Rename: F2 重命名符号

**新增 analysis 模块**
- collect_symbols: AST 遍历收集符号
- find_declaration/find_all_references: Token 扫描定位声明和引用

aster-core/examples/builtins.ast

@@ -0,0 +1,21 @@
+// Quick smoke test for new builtins
+print("--- len ---")
+print(len("hello"))
+print(len([1, 2, 3]))
+print(len({a: 1, b: 2, c: 3}))
+
+print("--- typeof ---")
+print(typeof(42))
+print(typeof("hi"))
+print(typeof(true))
+print(typeof(nil))
+print(typeof([1, 2]))
+print(typeof({a: 1}))
+print(typeof(print))
+
+print("--- push/pop ---")
+let arr = [1, 2]
+print("push:", push(arr, 3))
+print("arr:", arr)
+print("pop:", pop(arr))
+print("arr:", arr)