fix(rest): escape the NUL batch-dedup separator + regenerate batch docs reference

CI follow-up on the cross-object batch hardening (#1604):

- The per-op (object, action) dedup key in the /batch handler used a raw NUL
  (0x00) byte as its separator, which trips the check:nul-bytes gate (a raw NUL
  makes the file read as binary to grep/ripgrep). Replaced with the standard
  unicode NUL escape sequence, matching the convention already used for the
  exec-ctx memo key elsewhere in rest-server.ts. Byte-identical at runtime.
- Regenerated content/docs/references/api/batch.mdx (generated from the Zod
  spec) so it documents the new CrossObjectBatch* schemas — the check:docs gate
  requires the reference to track packages/spec.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015DgfsaEfmwVAY1SsPtQJ6U

Author: claude

content/docs/references/api/batch.mdx

@@ -30,8 +30,8 @@ Industry alignment: Salesforce Bulk API, Microsoft Dynamics Bulk Operations
 ## TypeScript Usage
 
 ```typescript
-import { BatchConfig, BatchOperationResult, BatchOperationType, BatchOptions, BatchRecord, BatchUpdateRequest, BatchUpdateResponse, DeleteManyRequest, UpdateManyRequest } from '@objectstack/spec/api';
-import type { BatchConfig, BatchOperationResult, BatchOperationType, BatchOptions, BatchRecord, BatchUpdateRequest, BatchUpdateResponse, DeleteManyRequest, UpdateManyRequest } from '@objectstack/spec/api';
+import { BatchConfig, BatchOperationResult, BatchOperationType, BatchOptions, BatchRecord, BatchUpdateRequest, BatchUpdateResponse, CrossObjectBatchOperation, CrossObjectBatchRequest, CrossObjectBatchResponse, DeleteManyRequest, UpdateManyRequest } from '@objectstack/spec/api';
+import type { BatchConfig, BatchOperationResult, BatchOperationType, BatchOptions, BatchRecord, BatchUpdateRequest, BatchUpdateResponse, CrossObjectBatchOperation, CrossObjectBatchRequest, CrossObjectBatchResponse, DeleteManyRequest, UpdateManyRequest } from '@objectstack/spec/api';
 
 // Validate data
 const result = BatchConfig.parse(data);
@@ -135,6 +135,43 @@ const result = BatchConfig.parse(data);
 | **results** | `{ id?: string; success: boolean; errors?: { code: string; message: string; category?: string; details?: any; … }[]; data?: Record<string, any>; … }[]` | ✅ | Detailed results for each record |
 
 
+---
+
+## CrossObjectBatchOperation
+
+### Properties
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **object** | `string` | ✅ | Target object (table) name |
+| **action** | `Enum<'create' \| 'update' \| 'delete'>` | ✅ | Operation to perform (default: create) |
+| **id** | `string` | optional | Target record id — required for update and delete |
+| **data** | `Record<string, any>` | optional | Record payload for create/update; a value may be `{ $ref: <opIndex> }` to reference an earlier op's created id |
+
+
+---
+
+## CrossObjectBatchRequest
+
+### Properties
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **operations** | `{ object: string; action: Enum<'create' \| 'update' \| 'delete'>; id?: string; data?: Record<string, any> }[]` | ✅ | Ordered operations executed in one transaction |
+| **atomic** | `boolean` | ✅ | Always true — the cross-object batch is all-or-nothing |
+
+
+---
+
+## CrossObjectBatchResponse
+
+### Properties
+
+| Property | Type | Required | Description |
+| :--- | :--- | :--- | :--- |
+| **results** | `any[]` | ✅ | Per-operation result, index-aligned with the request operations |
+
+
 ---
 
 ## DeleteManyRequest

packages/rest/src/rest-server.ts

@@ -6103,7 +6103,7 @@ export class RestServer {
                         const byName = new Map<string, any>(items.map((o: any) => [o?.name, o]));
                         const checked = new Set<string>();
                         for (const op of ops) {
-                            const key = `${op.object}
+                            const key = `${op.object}\u0000${op.action}`;
                             if (checked.has(key)) continue;
                             checked.add(key);
                             const obj = byName.get(op.object);