Port Carousel from 7.x

**Source**: Microsoft.Toolkit.Uwp.UI.Controls (7.x)
**Destination**: TBD (not yet determined)

## Description

An ItemsControl implementation that displays items in a smooth carousel layout.

## Prerequisites

None identified.

## Porting Basics

- [ ] Namespace updated to `CommunityToolkit.WinUI.*`
- [ ] Code for UWP, WinUI3 and Uno Platform consolidated
- [ ] Desired MultiTargets configured
- [ ] Sample code migrated
- [ ] Concept docs migrated
- [ ] Tests migrated and passing

## Quality Evaluation

See [Porting Criteria](https://github.com/CommunityToolkit/Windows/wiki/Component-Quality-Evaluation) for detailed evaluation guidance.

- [ ] UX: Accessibility reviewed
- [ ] UX: Visual design reviewed
- [ ] UX: Interaction patterns appropriate
- [ ] DX: API surface reviewed
- [ ] DX: API flexibility appropriate
- [ ] DX: Documentation updated
- [ ] MX: Breaking changes documented
- [ ] MX: Domain isolation appropriate
- [ ] MX: Test coverage adequate

## Tracking Gaps

*No gaps identified — porting work not yet started.*

## Closing

- [ ] All Porting Basics complete
- [ ] Quality Evaluation reviewed
- [ ] Gaps filed as sub-issues

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## 7x Documentation Inventory

**Docs ported to 8x**: n/a

**Docs not in 8x**: All sections

## 7x Source Inventory

**Source already ported to 8x**: n/a

**Source not ported to 8x**: All

## Notes

- Not currently planned for porting. Open to community interest.
- **Technical consideration**: Would require full rewrite to use ItemsRepeater API.
- **Archive redirect**: https://learn.microsoft.com/en-us/dotnet/communitytoolkit/windows/archive/carousel

まず、Microsoft.Toolkit.Uwp.UI.Controls 7.x Carousel のソースと、リンクされている Porting Criteria を確認します。移行先は引き続き TBD で、ソースファイルやテストは指定されておらず、issue には ItemsRepeater を使用した全面的な書き直しが実装に必要になると記載されています。完了とするには、記載されている移植、品質、ドキュメント、テストのチェックリストをすべて完了する必要があります。

索引モデルが issue の本文から書いたものです。