fix(ui): add chatHistoryTruncated to AppViewState type

Made-with: Cursor

ui/src/ui/app-view-state.ts

@@ -72,6 +72,7 @@ export type AppViewState = {
   fallbackStatus: FallbackStatus | null;
   chatAvatarUrl: string | null;
   chatThinkingLevel: string | null;
+  chatHistoryTruncated?: boolean;
   chatModelOverrides: Record<string, ChatModelOverride | null>;
   chatModelsLoading: boolean;
   chatModelCatalog: ModelCatalogEntry[];