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/extension.js

@@ -0,0 +1,43 @@
+const path = require('path');
+const { LanguageClient, TransportKind } = require('vscode-languageclient/node');
+
+/** @type {LanguageClient} */
+let client;
+
+/**
+ * @param {import('vscode').ExtensionContext} context
+ */
+function activate(context) {
+    const isWindows = process.platform === 'win32';
+    const serverExe = isWindows ? 'aster-lsp.exe' : 'aster-lsp';
+
+    // __dirname resolves to the real filesystem path (following the junction),
+    // so .. goes to the workspace root where target/ lives
+    const serverPath = path.join(__dirname, '..', 'target', 'debug', serverExe);
+
+    const serverOptions = {
+        command: serverPath,
+        args: [],
+    };
+
+    const clientOptions = {
+        documentSelector: [{ scheme: 'file', language: 'aster' }],
+    };
+
+    client = new LanguageClient(
+        'aster-lsp',
+        'Aster Language Server',
+        serverOptions,
+        clientOptions
+    );
+
+    client.start();
+}
+
+function deactivate() {
+    if (client) {
+        return client.stop();
+    }
+}
+
+module.exports = { activate, deactivate };