修复: read_symbol 搜不到 const 声明的符号

- 新增 variable_declarator 到 DEFINITION_KINDS
- Vue 3 + TS 大量使用 const fn = () => {} 箭头函数
  AST 节点是 variable_declarator，原本不在列表中
  导致 read_symbol 对 Vue 文件频繁 fallback 回 read_file

src-tauri/src/commands/ai/code_intel.rs

@@ -39,6 +39,8 @@ const DEFINITION_KINDS: &[&str] = &[
     "interface_declaration",
     "enum_declaration",
     "method_definition",
+    // TS/JS const/let/var 声明(如 const fn = () => {})
+    "variable_declarator",
     // Go
     "method_declaration", // Go method(receiver func)
     "type_declaration",   // Go type Xxx struct/interface/func