fix(12.2): close code-review blockers on uploads, JSON caps, and pivot fill

Keep form save behind in-flight uploads, make retries idempotent via X-Upload-Id, cap remaining JSON bodies, and surface pending pivot type errors instead of zeroing them.

Co-authored-by: Cursor <cursoragent@cursor.com>

admin/src/api/files.ts

@@ -37,9 +37,12 @@ export interface UploadHandle {
 export type UploadProgress = (loaded: number, total: number) => void
 
 /** Everything a fileupload control does with its files. */
+/** Client upload id sent as X-Upload-Id so a retry returns the stored file. */
+export const UPLOAD_ID_HEADER = 'X-Upload-Id'
+
 export interface FileRoutes {
   list(): Promise<FileCallResult<FileItem[]>>
-  upload(file: File, onProgress?: UploadProgress): UploadHandle
+  upload(file: File, onProgress?: UploadProgress, uploadId?: string): UploadHandle
   update(file: number, body: AdminFileCaptionRequest): Promise<FileCallResult<FileItem>>
   remove(file: number): Promise<FileCallResult<FileMutationResult>>
   reorder(ids: number[]): Promise<FileCallResult<FileItem[]>>
@@ -137,6 +140,7 @@ export function uploadWithProgress(
   file: File,
   headers: Record<string, string>,
   onProgress?: UploadProgress,
+  uploadId?: string,
 ): UploadHandle {
   let current: XMLHttpRequest | null = null
   let aborted = false
@@ -151,6 +155,9 @@ export function uploadWithProgress(
       for (const [name, value] of Object.entries(headers)) {
         request.setRequestHeader(name, value)
       }
+      if (uploadId) {
+        request.setRequestHeader(UPLOAD_ID_HEADER, uploadId)
+      }
       request.upload.onprogress = (event: ProgressEvent) => {
         if (event.lengthComputable) {
           onProgress?.(event.loaded, event.total)
@@ -208,7 +215,7 @@ export function parentFileRoutes(
   const url = `${controllerUrl(source)}/${segment(recordId)}/files/${segment(field)}`
   return {
     list: () => settle(() => api.GET('/{vendor}/{plugin}/{controller}/{id}/files/{field}', { params: { path, header } })),
-    upload: (file, onProgress) => uploadWithProgress(url, file, { ...header }, onProgress),
+    upload: (file, onProgress, uploadId) => uploadWithProgress(url, file, { ...header }, onProgress, uploadId),
     update: (file, body) =>
       settle(() =>
         api.PUT('/{vendor}/{plugin}/{controller}/{id}/files/{field}/{file}', {
@@ -273,7 +280,7 @@ export function childFileRoutes(
           params: { path, header },
         }),
       ),
-    upload: (file, onProgress) => uploadWithProgress(url, file, { ...header }, onProgress),
+    upload: (file, onProgress, uploadId) => uploadWithProgress(url, file, { ...header }, onProgress, uploadId),
     update: (file, body) =>
       settle(() =>
         api.PUT('/{vendor}/{plugin}/{controller}/{id}/relations/{name}/records/{child}/files/{field}/{file}', {