Fix UI stop button delay by using Next.js after() for background chat summaries

vibn-frontend/app/api/chat/route.ts

@@ -14,7 +14,7 @@
  *   data: {"type":"done"}
  *   data: {"type":"error","error":"..."}
  */
-import { NextResponse } from "next/server";
+import { NextResponse, after } from "next/server";
 import { requireWorkspacePrincipal } from "@/lib/auth/workspace-auth";
 import { query, queryOne } from "@/lib/db-postgres";
 import { callVibnChat, streamVibnChat } from "@/lib/ai/vibn-chat-model";
@@ -628,22 +628,21 @@ function extractPreviewUrl(messages: ChatMessage[]): string | undefined {
   return undefined;
 }
 
-
 function summarizeForUI(raw: string): string {
   try {
     const p = JSON.parse(raw);
     if (p && typeof p === "object") {
       const clone = { ...p };
       // Strip massive payload fields so the UI gets intact JSON
-      if (clone.result && typeof clone.result === 'object') {
+      if (clone.result && typeof clone.result === "object") {
         if (clone.result.log) clone.result.log = "...";
         if (clone.result.content) clone.result.content = "...";
         if (clone.result.listing) clone.result.listing = "...";
       }
-      if (typeof clone.stdout === 'string' && clone.stdout.length > 200) {
+      if (typeof clone.stdout === "string" && clone.stdout.length > 200) {
         clone.stdout = clone.stdout.slice(0, 200) + "...";
       }
-      if (typeof clone.stderr === 'string' && clone.stderr.length > 200) {
+      if (typeof clone.stderr === "string" && clone.stderr.length > 200) {
         clone.stderr = clone.stderr.slice(0, 200) + "...";
       }
       return JSON.stringify(clone);
@@ -1898,7 +1897,7 @@ export async function POST(request: Request) {
         // Wrapped in try/catch + .catch — the response stream is already
         // closed and we don't want a summary failure to surface as an
         // error to the user.
-        (async () => {
+        after(async () => {
           try {
             const allMessages = [...history, finalMsg];
             // Only summarize if there's something worth summarizing.
@@ -1951,7 +1950,7 @@ export async function POST(request: Request) {
           } catch {
             // best-effort; silent failure
           }
-        })().catch(() => {});
+        });
 
         // Plan extraction is handled inline during tool calls or proactively.
         emit({ type: "done" });