fix: 时间显示/3D线置顶强调/子标签页重构

1. fix(HeroSection): period 为 {zh,en} 对象却直接渲染导致显示 [object Object]，
   改为字符串 '2022'
2. feat(timeline): 3D滚球(最终形态)线移到最前并 featured 强调(渐变背景+★+实心3D徽章)，
   其后用分隔标记提示「早期并行演进：2D线」
3. refactor(MobileGame): 团队+排行榜/迭代记录/实验 改为平级子标签页(SubTabs)，
   默认显示团队+排行榜；新增 SubTabs.vue 通用子标签组件
   headless 验证：默认页(团队+排行榜) -> 迭代记录(时间线) -> 实验(视频) -> 切回 全通过，
   中英文子标签页文案正常

src/modules/mobile-game/data/versions.js

@@ -9,6 +9,16 @@
 // track 字段标识所属演进线；form 标识 2D/3D；order 用于时间线排序（按发布先后）。
 
 export const tracks = [
+  {
+    id: 'roll-a-ball',
+    name: { zh: '3D 滚球（最终形态）', en: '3D Rolling Ball (Final Form)' },
+    form: '3D',
+    featured: true,
+    desc: {
+      zh: '项目从 2D 转向 3D 的最终形态。手机陀螺仪倾斜操控滚球，含雪花砖掉落、黄色砖弹跳等机制。',
+      en: 'The final form as the project shifted from 2D to 3D. Tilt the phone to roll the ball; snowflake bricks fall, yellow bricks bounce.'
+    }
+  },
   {
     id: 'zikai-ui',
     name: { zh: 'zikai-ui 角色控制器', en: 'zikai-ui Character Controller' },
@@ -35,15 +45,6 @@ export const tracks = [
       zh: '2D 横版平台跳跃，吃金币、计分、血量、触屏摇杆。',
       en: '2D side-scrolling platformer: collect coins, score, health, touch joystick.'
     }
-  },
-  {
-    id: 'roll-a-ball',
-    name: { zh: '3D 滚球（最终形态）', en: '3D Rolling Ball (Final Form)' },
-    form: '3D',
-    desc: {
-      zh: '项目从 2D 转向 3D 的最终形态。手机陀螺仪倾斜操控滚球，含雪花砖掉落、黄色砖弹跳等机制。',
-      en: 'The final form as the project shifted from 2D to 3D. Tilt the phone to roll the ball; snowflake bricks fall, yellow bricks bounce.'
-    }
   }
 ]