fix: switch user_main invocation to use keyword arguments for better default parameter handling (#6756)

* fix: switch user_main invocation to use keyword arguments for better default parameter handling

* fix: test

---------

Co-authored-by: archer <545436317@qq.com>

projects/code-sandbox/test/compat/legacy-python.test.ts

@@ -99,6 +99,16 @@ def main(name, age):
     expect(result.data?.codeReturn.msg).toBe('Hello, World!');
   });
 
+  it('main 前置命名参数缺失但有默认值，后置参数仍按 kwargs 注入', async () => {
+    const result = await pool.execute({
+      code: `def main(a=None, b=None):
+    return {"a": a if a else "无", "b": b if b else "无"}`,
+      variables: { b: 'd2' }
+    });
+    expect(result.success).toBe(true);
+    expect(result.data?.codeReturn).toEqual({ a: '无', b: 'd2' });
+  });
+
   // ===== 返回值类型兼容 =====
 
   it('返回列表（旧版常见）', async () => {

projects/code-sandbox/test/unit/security.test.ts

@@ -25,8 +25,8 @@ beforeAll(async () => {
 });
 
 afterAll(async () => {
-  await jsPool.shutdown();
-  await pyPool.shutdown();
+  await jsPool?.shutdown();
+  await pyPool?.shutdown();
 });
 
 describe('模块拦截', () => {