fix(vip): render points exchange description

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/widget-system/vip-settings-structured-contract.test.cjs

@@ -371,6 +371,7 @@ test('运行时归一化：默认值、价格净化、零价与非法行剔除',
   assert.strictEqual(custom.upgrade.permanent_tag_class, 'jb-vip2');
   // 积分兑换：非法行（积分为 0 / 等级越界 / 时长为空）被剔除。
   assert.strictEqual(custom.points_exchange.packages.length, 3);
+  assert.strictEqual(custom.points_exchange.desc, '<p>积分兑换说明</p>');
   assert.strictEqual(custom.points_exchange.packages[0].days, 30);
   assert.strictEqual(custom.points_exchange.packages[1].is_permanent, true);
   assert.strictEqual(custom.points_exchange.packages[2].days, 90);