fix: close PI core chat review gaps

src/lib/coding-attachments.ts

@@ -1,6 +1,8 @@
 import { hostApiFetch, hostApiFetchBytes } from './host-api';
 
 export const CODING_ATTACHMENT_MAX_BYTES = 16 * 1024 * 1024;
+export const CODING_ATTACHMENT_MAX_COUNT = 16;
+export const CODING_ATTACHMENT_UPLOAD_CONCURRENCY = 4;
 export const CODING_ATTACHMENT_MIMES = new Set([
   'image/png',
   'image/jpeg',