Revert "feat(threads): paginate full history via summaries endpoint (#1022)" (#1037)

This reverts commit 2f47f1ced2.

frontend/src/core/threads/utils.ts

@@ -1,5 +1,6 @@
 import type { Message } from "@langchain/langgraph-sdk";
 
+import type { AgentThread } from "./types";
 
 export function pathOfThread(threadId: string) {
   return `/workspace/chats/${threadId}`;
@@ -18,6 +19,6 @@ export function textOfMessage(message: Message) {
   return null;
 }
 
-export function titleOfThread(thread: { values?: { title?: string | null } | null }) {
+export function titleOfThread(thread: AgentThread) {
   return thread.values?.title ?? "Untitled";
 }