feat: show changed files after completed turns

Add changed-file pills with per-file diff stats
Add a chat setting to disable the feature fully
Avoid changed-file projection work when disabled

packages/ui/src/lib/api/types.ts

@@ -651,6 +651,7 @@ export interface SettingsPayload {
   showOpenCodeUpdateNotifications?: boolean;
   openCodeUpdateToastDismissedVersion?: string;
   showToolFileIcons?: boolean;
+  showTurnChangedFiles?: boolean;
   showExpandedBashTools?: boolean;
   showExpandedEditTools?: boolean;
   chatRenderMode?: 'sorted' | 'live';