refactor: extract SettingsPageHost and optimize split-layout transitions for nested settings pages

[cwuom]

• 优化设置页面在分屏布局下的切换行为，复用导航面板并清理离开的详情页。
• 仅在相邻页面之间播放横向过渡动画。
• 保留嵌套设置页面切换期间的动画效果。
• 为设置页面导航项补充选中状态和测试标签。
• 新增 Compose UI 测试，覆盖导航复用、详情页切换、选中状态同步、动画保留和旧页面清理。

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 26e5667 and 2477627.

📒 Files selected for processing (3)

• app/src/androidTest/java/moe/ouom/neriplayer/ui/screen/tab/SettingsPageHostTest.kt
• app/src/main/java/moe/ouom/neriplayer/ui/screen/tab/SettingsScreen.kt
• app/src/main/java/moe/ouom/neriplayer/ui/screen/tab/settings/page/MiuixSettingsScaffold.kt

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📝 Walkthrough

Walkthrough

新增 SettingsPageHost，统一处理设置页面的分栏渲染和非分栏页面过渡。调整详情页动画条件，并支持无动画切换。为设置页面行添加测试标签和 selected 语义。新增 Compose UI 测试，覆盖导航面板复用、详情页清理、选中状态同步及嵌套页面动画。

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	标题准确概括了提取SettingsPageHost及优化分屏嵌套设置页过渡的主要变更。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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