introduces workspace items as combined search+chat model

tui/src/types.ts

@@ -29,6 +29,16 @@ export type SearchSummary = {
   updatedAt: string;
 };
 
+export type ChatWorkspaceItem = ChatSummary & {
+  type: "chat";
+};
+
+export type SearchWorkspaceItem = SearchSummary & {
+  type: "search";
+};
+
+export type WorkspaceItem = ChatWorkspaceItem | SearchWorkspaceItem;
+
 export type Message = {
   id: string;
   createdAt: string;