fix(frontend): preserve agent context in thread history routes (#1771)

* fix(frontend): preserve agent context in thread history routes

* fix(frontend): preserve agent thread fallback context

* style(frontend): format thread route utils test

---------

Co-authored-by: luoxiao6645 <luoxiao6645@gmail.com>

frontend/src/core/threads/utils.test.ts

@@ -0,0 +1,33 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+const { pathOfThread } = await import(
+  new URL("./utils.ts", import.meta.url).href
+);
+
+void test("uses standard chat route when thread has no agent context", () => {
+  assert.equal(pathOfThread("thread-123"), "/workspace/chats/thread-123");
+  assert.equal(
+    pathOfThread({
+      thread_id: "thread-123",
+    }),
+    "/workspace/chats/thread-123",
+  );
+});
+
+void test("uses agent chat route when thread context has agent_name", () => {
+  assert.equal(
+    pathOfThread({
+      thread_id: "thread-123",
+      context: { agent_name: "researcher" },
+    }),
+    "/workspace/agents/researcher/chats/thread-123",
+  );
+});
+
+void test("uses provided context when pathOfThread is called with a thread id", () => {
+  assert.equal(
+    pathOfThread("thread-123", { agent_name: "ops agent" }),
+    "/workspace/agents/ops%20agent/chats/thread-123",
+  );
+});