feat: 优化代码节点 main 编写体验

- 更新代码节点帮助、占位示例与补全片段

- 保留 _result 旧版兼容提示并补充补全测试

easyflow-ui-admin/packages/tinyflow-ui/src/components/utils/codeCompletion.test.ts

@@ -52,6 +52,25 @@ describe('codeCompletion utils', () => {
     ).toBe(true);
   });
 
+  it('should prefer main return snippets for javascript output', () => {
+    const completions = createBusinessCompletions('javascript', []);
+    const mainCompletion = completions.find((item) => item.label === 'main');
+    const resultCompletion = completions.find(
+      (item) => item.label === 'result-object',
+    );
+
+    expect(mainCompletion).toMatchObject({
+      type: 'snippet',
+      detail: '代码节点入口',
+      boost: 1000,
+    });
+    expect(String(mainCompletion?.apply)).toContain('function main');
+    expect(String(mainCompletion?.apply)).toContain('return {');
+    expect(String(resultCompletion?.apply)).toBe(
+      "return { message: 'ok', data };",
+    );
+  });
+
   it('should detect blocked nodes for comment/string/property contexts', () => {
     expect(shouldSkipBusinessCompletion('Comment')).toBe(true);
     expect(shouldSkipBusinessCompletion('LineComment')).toBe(true);