fix: preserve plugin tool state.attachments in UI and materializer (#2367)

* preserve attachments in UI and materializer

* add support for non-image attachments

* preserve attachments in UI and materializer

* improve attachment rendering and state synchronization

* simplify attachment filtering and key handling

* prevent rendering tool attachments without URLs

* require `f.url` in `imageAttachments` to match gallery indices

packages/ui/src/lib/i18n/messages/ja.ts

@@ -2068,6 +2068,7 @@ export const dict: Record<I18nKey, string> = {
   'chat.toolPart.copiedOutput': '出力をコピーしました',
   'chat.toolPart.copyOutputFailed': '出力のコピーに失敗しました',
   'chat.toolPart.openSubtask': '{type}サブタスクを開く',
+  'chat.toolPart.attachmentFallback': '添付ファイル',
   'chat.todo.total': '合計',
   'chat.todo.inProgress': '進行中',
   'chat.todo.pending': '保留中',