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

vscode-ext/language-configuration.json

@@ -0,0 +1,26 @@
+{
+    "comments": {
+        "lineComment": "//",
+        "blockComment": ["/*", "*/"]
+    },
+    "brackets": [
+        ["{", "}"],
+        ["[", "]"],
+        ["(", ")"]
+    ],
+    "autoClosingPairs": [
+        { "open": "{", "close": "}" },
+        { "open": "[", "close": "]" },
+        { "open": "(", "close": ")" },
+        { "open": "\"", "close": "\"" },
+        { "open": "'", "close": "'" }
+    ],
+    "surroundingPairs": [
+        ["{", "}"],
+        ["[", "]"],
+        ["(", ")"],
+        ["\"", "\""],
+        ["'", "'"]
+    ],
+    "wordPattern": "[a-zA-Z_][a-zA-Z0-9_]*"
+}