重构聊天会话管理，支持会话历史和存储

src/lib/chatStream.ts

@@ -4,6 +4,7 @@ import { config } from "@config/config";
 export type StreamEvent =
   | { type: "token"; sessionId: string; content: string }
   | { type: "done"; sessionId: string }
+  | { type: "session_title"; sessionId: string; title: string }
   | {
       type: "progress";
       sessionId: string;
@@ -182,6 +183,12 @@ export const streamAgentChat = async ({
             type: "done",
             sessionId: parsed.session_id ?? "",
           });
+        } else if (event === "session_title") {
+          onEvent({
+            type: "session_title",
+            sessionId: parsed.session_id ?? "",
+            title: typeof parsed.title === "string" ? parsed.title : "",
+          });
         } else if (event === "error") {
           onEvent({
             type: "error",