Fix duplicated file changes for background sessions

When chat.checkpoints.showFileChanges is enabled, only show
file changes summary for local sessions since background sessions
already have their own file changes part registered.

Co-authored-by: osortega <[email protected]>

Author: Copilot

src/vs/workbench/contrib/chat/browser/chatListRenderer.ts

@@ -59,6 +59,8 @@ import { IChatChangesSummaryPart, IChatCodeCitations, IChatErrorDetailsPart, ICh
 import { getNWords } from '../common/chatWordCounter.js';
 import { CodeBlockModelCollection } from '../common/codeBlockModelCollection.js';
 import { ChatAgentLocation, ChatConfiguration, ChatModeKind, CollapsedToolsDisplayMode, ThinkingDisplayMode } from '../common/constants.js';
+import { localChatSessionType } from '../common/chatSessionsService.js';
+import { getChatSessionType } from '../common/chatUri.js';
 import { MarkUnhelpfulActionId } from './actions/chatTitleActions.js';
 import { ChatTreeItem, IChatCodeBlockInfo, IChatFileTreeInfo, IChatListItemRendererOptions, IChatWidgetService } from './chat.js';
 import { ChatAgentHover, getChatAgentHoverOptions } from './chatAgentHover.js';
@@ -1163,7 +1165,9 @@ export class ChatListItemRenderer extends Disposable implements ITreeRenderer<Ch
 	}
 
 	private shouldShowFileChangesSummary(element: IChatResponseViewModel): boolean {
-		return element.isComplete && this.configService.getValue<boolean>('chat.checkpoints.showFileChanges');
+		// Only show file changes summary for local sessions - background sessions already have their own file changes part
+		const isLocalSession = getChatSessionType(element.sessionResource) === localChatSessionType;
+		return element.isComplete && isLocalSession && this.configService.getValue<boolean>('chat.checkpoints.showFileChanges');
 	}
 
 	private getDataForProgressiveRender(element: IChatResponseViewModel) {