Honor identity sort orders for Arrow table writes

## Feature Request / Improvement

PyIceberg accepts table sort orders at write time but ignores them. Arrow table writes produce unsorted data files and hard-code `sort_order_id=None`, so manifests are inconsistent with the sort order the user declared.

Related umbrella issue: #271

### Use case / motivation

Without a truthful sort_order_id and physically ordered data files, readers can't use sort-order-aware pruning and the manifest disagrees with the table's sort metadata. Users who declare a sort order expect their writes to honor it.

### Proposed change

When every sort field uses an identity transform and null placement is consistent, sort materialized Arrow table writes. Unpartitioned tables are sorted before bin packing and each final partition is sorted independently. The table's sort-order ID is recorded on the data files.

Unsupported transforms, nested or missing fields, mixed null placement, and streaming RecordBatchReader writes keep the current behavior. Files are marked unsorted and sort_order_id stays null, with a warning explaining why.

### Implementation

PR #3830 sorts the writes, carries the sort-order ID through WriteTask, writes the truthful DataFile.sort_order_id, and includes unit and integration coverage.

### Tooling note

I developed this with assistance from DS v4 Pro and reviewed the changes myself.

### References

- #271
- #3830

まず PR #3830 を確認し、Arrow table writes のために追加される unit および integration のカバレッジも確認してください。sort-order IDs、WriteTask、DataFile、manifests、bin packing がどのように扱われるかを確認してください。対応している identity-sort writes が、正しい sort_order_id 値を持つ順序付けされたファイルを生成し、非対応のケースでは現在の動作と警告が維持されれば完了です。

索引モデルが issue の本文から書いたものです。